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Splitting stars – for us and for you!

We are experienced amateur astronomers who especially enjoy viewing double stars with long-focus refractors.  This journal is a record of our observations, but we also hope it will serve as a guide to you to help you plan observing sessions and choose double stars you want to observe.  In the column to the left you’ll find a drop down menu listing the doubles in this blog by constellation – and to the right there’s a list of our 10 most recent observations. Finally, you have two other choices:

  • First, you can read  our observations of a double and leave your own observations of that same star as a comment.
  • Second, you can subscribe to this blog so that you get email notifications when we add a star to it. Just check out the links in the right-hand column.

We’d love to hear from you regarding your own observations of the same doubles.

Wrestling on a Herculean Mat: A Tale of Two Close Encounters — OΣ 344 (with Σ 2290) and Zeta (ζ) Herculis

OK, it’s time to put away the low power eyepieces and aperture-challenged optical devices and get serious about prying into the diabolically difficult and totally torturous realm of high Delta doubles. Those would be doubles with magnitude differences of roughly two magnitudes or more. And to keep things manageable and sane, we’ll stay away from any pairs fainter than fifteenth magnitude. ;)

But in reality we don’t need to go anywhere near that faint – not that we ever could anyway – because the two stars we’re going to look at here are more than capable of making us yearn for less challenging targets such as Albireo or Mizar. In fact, keep a bottle of aspirin handy – you may need to subdue a headache caused by high-frequency stellar spinning-hopping-and-twitching.

We’re going to start way up high in the northeastern corner of Hercules with an enticingly innocent 6.47 magnitude star dubbed OΣ 344 by its discoverer, Otto Struve, and then re-dubbed STT 344 by the Washington Double Star Catalog (WDS).  If you didn’t know there was a tenth magnitude companion hovering near that 6.47 bundle of photons, you probably would skip right over it – which just goes to show there are times when ignorance can truly be bliss.

But since the fate of a double star addict is to be cursed with a surplus knowledge of numerical data, we’ve got no choice but to stop and take a peek.

Hang on tight.

Zeta (ζ) Herculis, the second star we’ll look at, is easily found at the southwest corner of the distinctive Hercules Keystone asterism. The star we’re in search of now, OΣ 344, is hiding two and a half degrees southeast of Gamma (γ) Draconis. Since it’s three and half magnitudes fainter than Zeta (ζ) Herculis, we’ll need another chart to locate it. (Stellarium screen image with labels added, click to enlarge).

Zeta (ζ) Herculis, the second star we’ll look at, is easily found at the southwest corner of the distinctive Hercules Keystone asterism. The star we’re in search of now, OΣ 344, is hiding two and a half degrees southeast of Gamma (γ) Draconis. Since it’s three and half magnitudes fainter than Zeta (ζ) Herculis, we’ll need another chart to locate it. (Stellarium screen image with labels added, click to enlarge).

We’ll start at second magnitude Gamma (γ) Draconis and move east and slightly south for a distance of 1° 45’, to 6.3 magnitude HIP 88732. Then we’ll cross the border into Hercules by making a half degree jump directly southeast to 7.3 magnitude HIP 88975 (also known as HU 674, a tight pair we’ll avoid since it’s separated by .52”).   Now hop just short of a degree (48’) southwest to our goal, 6.5 magnitude OΣ 344, which is at the north end of a faint, but distinctive, group of three seventh and eighth magnitudes stars. Be careful not to land on another similarly configured, but wider, group of four stars located another degree to the southwest.   I’ve labeled the northern member of that group, 6.2 magnitude HIP 88415 (also known as Σ 2277, which we’ll come back to in another post). (Stellarium screen image with labels added, click on the chart for a larger view).

We’ll start at second magnitude Gamma (γ) Draconis and move east and slightly south for a distance of 1° 45’, to 6.3 magnitude HIP 88732. Then we’ll cross the border into Hercules by making a half degree jump directly southeast to 7.3 magnitude HIP 88975 (also known as HU 674, a tight pair we’ll avoid since it’s separated by .52”). Now hop just short of a degree (48’) southwest to our goal, 6.5 magnitude OΣ 344, which is at the north end of a faint, but distinctive, group of three seventh and eighth magnitudes stars. Be careful not to land on another similarly configured, but wider, group of four stars located another degree to the southwest. I’ve labeled the northern member of that group, 6.2 magnitude HIP 88415 (also known as Σ 2277, which we’ll come back to in another post). (Stellarium screen image with labels added, click on the chart for a larger view).

OΣ 344 (STT 344)             HIP: 88754   SAO: 47233
RA: 18h 07.1m   Dec: +49° 43’
Magnitudes: 6.47, 10.31
Separation:  2.3”
Position Angle: 140° (WDS 2009)
Distance: 722 Light Years
Spectral Classification:  “A” is  A2

I was first made aware of the existence of OΣ 344 after wrestling two difficult high Delta pairs to a dubious draw in Ursa Major (namely Bu 1074 and Cou 1900) when Mark McPhee posted a comment about it – something like “If you’d like a taste of what Cou 1900 is supposed to offer, mosey over to STT 344 in Hercules – you won’t be disappointed.”  Now that’s like waving a dog-eared first edition copy of Burnham’s 1906 double star catalog in front of me, but I had to wait until seeing conditions aligned with the stars, so to speak.   It took most of a year, but I finally had my chance – and this is what things looked like on first approach:

As I said, very innocent looking – just another six-plus magnitude star beaming its white photons into a fairly sparse field. (East and west are reversed here to match the SCT view).

As I said, very innocent looking – just another six-plus magnitude star beaming its white photons into a fairly sparse field.  Note the location of ninth magnitude SAO 47230 — we’re going to need that later.  (East and west are reversed here to match the SCT view, click on the sketch to enlarge it).

So there I sat, parked permanently (at least it had begun to seem that way) in upper northeast Hercules, attempting to wrestle frantically wriggling white photons into a stationary image for long enough to visually grab that 10.31 magnitude secondary. Seeing conditions were OK – certainly not worth bowing to the sky gods for – but I had a hunch there was a chance.  The image in a 10mm Radian (245x) didn’t divulge anything, but since the frantic wriggle wasn’t high frequency yet, I reached for what is usually my ace-in-the-hole ocular, an old Celestron 7.5mm Plössl (327x) . . . . . and the wriggle not only advanced into high frequency territory, the image turned to mush. Suddenly I couldn’t buy a sharp focus with that eyepiece for all the Plössls on planet Earth.

Sometimes, though, there’s a different world lurking on the other side of that realm where visual images turn to mushy photons, so I reached for another dependable tool, a 6mm Astro-Tech Plössl. That eyepiece has always done an excellent job at controlling the glare in very glaring situations, such as this one.   And for who knows what reason, I was able to get its 408x image into focus – usually only briefly, but occasionally for several seconds at a time.

I sat patiently still, waiting and hoping for that magical secondarial sighting, while my tortured right eye grudgingly tolerated my obsession. After about fifteen minutes – I’m guessing since time becomes every bit as relative in this situation as Einstein predicted – I had an averted vision glimpse of something popping into view just inside the thick diffraction ring surrounding the primary.

Several times it leaped into sight and then slipped silently back into the primary’s high frequency twitch, and then re-appeared again.   After several of those teasing episodes, I grabbed the secondarial light with direct vision and held it for a couple of seconds:

Believe me, the image was nowhere near this stable.   (East & west reversed once again).

Believe me, the image was nowhere near this stable.  Click on the image to get a better view of the secondary. (East & west reversed once again).

Seeing conditions seemed to be improving slightly – either that, or my eyepiece eye and a secret compartment in my brain were getting better at cooperating with each other. At one point, I had the secondary in direct view for about ten seconds. It was a bit more than a puff of light – it had to be in order to be seen in the primary’s throbbing glare – but not quite what you would call a splendidly solid beam of light. At times there was almost a thinly transparent, surreal, quality to it.

But it was there – definitely, undeniably, unquestionably there – which was more than I had been able to say about the secondaries of Bu 1074 and Cou 1900 the year prior.

And as I sat there, mesmerized into a stellar stupor, I remembered another Herculean challenge – Zeta. But by the time I tore myself loose from Otto Struve’s 344th pair, the clouds began moving in, turning the sky into a featureless dark ocean. So I had to wait until the following night . . . . . . . and having wrestled unsuccessfully with Zeta numerous times the prior year, I reached for the 9.25 inch edge once again.

BUT – before you move your scope, we really should pan over to one of F.G.W. Struve’s nearby discoveries, Σ 2290, for a quick peek – it’s located a mere 18’ to the north. If you move OΣ 344 to the south edge of the field of view, Σ 2290 will come into view just slightly west of the north corner of the field. You can use 8.79 magnitude SAO 47230 to guide you in the correct direction.

Σ 2290         HIP: 88713   SAO: 30749
RA: 18h 06.6m   Dec: +50° 01’
Identifier                  Magnitudes          Separation        Position Angle        WDS
Cou 2276    Aa, Ab:  9.77, 10.00                0.30”                  13°                 1993
STF 2290         AB:  8.90, 11.20                3.90”                 352°                 2009
STF 2290         AC:  8.90, 12.70            178.00”                   69°                 2003
Distance: 2233 Light Years (Simbad)
Spectral Classification:  “A” is A5

The primary was a definite white, and the close-in eleventh magnitude secondary was easy to spot when the seeing cooperated and a real pain when it didn’t. The 12.70 magnitude “C” component, added to the system in 1880, is just a speck of light in the 9.25 inch SCT. You have to wonder why the 13th magnitude star one minute north of “C” wasn’t included at the same time.   (East & west reversed once more, click on the sketch for a much better version).

The primary was a definite white, and the close-in eleventh magnitude secondary was easy to spot when the seeing cooperated, and a real pain when it didn’t. The 12.70 magnitude “C” component, added to the system in 1880, is just a speck of light in the 9.25 inch SCT. You have to wonder why the 13th magnitude star one minute north of “C” wasn’t included at the same time. (East & west reversed once more, click on the sketch for a much better version).

Now that we have that one under our belts, we’ll move on to Zeta (ζ ) Herculis. If you’ve lost track of it, here’s the first chart once again.

Zeta (ζ) Herculis  (40 Her)  (Σ 2084)  (H I 36)
HIP: 81693   SAO: 65485
RA: 16h 41.3m   Dec: +31° 36’
Magnitudes: 2.95, 5.40
Separation:  1.186”
Position Angle: 145.5° (WDS 2014)
Distance: 35 Light Years
Spectral Classification: “A” is G0, “B” is G7
Note: Orbit and data can be seen here

I think it was Neil English, renowned guru of the long focus achromatic refractor, who first brought Zeta (ζ) Herculis to my attention — and here I was, attacking it with an SCT.   However, without giving too much away, after the evening with the SCT, I returned to the refractor fold with my six inch f/10 to get this wide field view of Zeta (ζ):

Again, a very sparse field, but enhanced marvelously by Zeta’s subtly hypnotizing gold/white glow that I find absolutely irresistible after two seasons of staring at it. (East and west reversed to match the refractor view).

Again, a very sparse field, but enhanced marvelously by Zeta’s subtly hypnotizing gold/white glow that I find absolutely irresistible after two seasons of staring at it. (East and west reversed to match the refractor view — click on the sketch to bring the gold glow to life).

To get back to the evening of June 23rd, I found the skies a couple of notches more cooperative, something close to a IV on this chart. I spent some time on other objects until close to midnight, which gave Zeta (ζ) plenty of time to get into position high in the sky and just west of the meridian. Once I located it and centered it in an 18mm Radian (136x), I went immediately to the 6mm Astro-Tech Plössl (408x) again. The image was more steady than the previous night, so it didn’t take long at all to realize the secondary was sitting out in the open, right at the outer edge of the first diffraction ring:

Apart from the welcome sight of the secondary, one of the things I quickly noticed was the pleasing gold/white photons characteristic of the low power view had been transformed into a thin, weak yellow.

Apart from the welcome sight of the secondary, one of the things I quickly noticed was the pleasing gold/white photons characteristic of the low power view had been transformed into a thin, weak yellow.  (East & west reversed, click on the sketch for a larger view).

I was amazed at how easy it was! I had tried and failed to split Zeta several times the previous year and here it was, just like that, on the first try. But now that I had the secondary in sight, I realized last year’s tantalizing teases were the real thing.  All those attempts had been under less than friendly seeing conditions, with so much jumping, whirling, spinning, and hopping that I could never be certain of what I saw.

When I returned to Zeta (ζ) a week later to get the wide field sketch with the 6 inch f/10 refractor, the seeing conditions were somewhere between the previous visit to Zeta (ζ) and the one to OΣ 344. I couldn’t resist the temptation to try again, so after I finished the 84x sketch, I reached for the 6mm AT Plössl (253x) once more to see what would happen. I had to look closely, but the secondary was definitely attempting to split off from the primary – what it needed was some help.

I grabbed a seldom-used 2.4x Dakin Barlow, slipped the 6mm AT Plössl into it, parked the whole thing in the diagonal, and then leaned over the unified pair and attempted to focus the blurred, vibrating image staring back at me. There’s one thing you just can’t miss when you blow up a yellowish 2.95 magnitude star to 608x – it’s dazzlingly bright. In fact, it seems to light up the whole field of view. With a very delicate touch on the two-speed focuser’s fine focus knob, I nudged the image toward what I hoped would be something resembling a focused star.

All the yellow-white light compressed into that diminutive five arc minute field was shimmering as though the star was about to erupt. Slowly, then suddenly, the image came into focus. I had to coax my eyepiece eye into reconnecting with the same secret compartment in my brain it had found on the night with OΣ 344, but after it re-established the connection, I could see through the glare to the secondary, sitting once more on the outer edge of the first diffraction ring with what looked like a mile of open space between it and the primary. OK – that’s a bit of an exaggeration caused by a temporary illusion and a very brief bout of insanity, but . . . . . . . . WOW! What a sight!

Double star nirvana! It seldom gets better than this! (East & west reversed once again).

Double star nirvana! It seldom gets better than this! (East & west reversed once again, click on the sketch to enlarge the gap between the primary and secondary).

William Herschel came up with a great phrase to describe the suddenly obvious distance between the primary and secondary at very high magnifications: “the distance is, as it were, laid open to the view.” You can almost see that thought materializing in his mind as he describes his experience with Zeta (ζ) on July 18th, 1782 (source, scroll down to the sixth title):

Notice those magnifications: 460x, 932x, and 811x! (The quote above is from the bottom of the same page as this observation).

Notice those magnifications: 460x, 932x, and 811x! (The quote above is from the bottom of the same page as this observation).

There’s nothing like the thrill of peering into the dazzle of magnified starlight and catching sight of a smaller secondary, very clear and very distinct, with black space between it and the primary, each of them vibrating, spinning, hopping, and leaping in unison – and around both of them, a diffraction ring shimmering so rapidly it appears to be spinning. It’s an electrical thrill that causes every quark in you to quiver (and probably quite a few outside you), and reminds you the sketch is only a snapshot of an experience quite literally out of this world.

Gotta go grab a small glass of something strong to calm the optic nerves now . . . . . . .

Clear (and stable) Skies!   :cool:  (Next time, back to northern Hercules again).

Caught in the Coma Cluster, Part 2: SHJ 143, HJ 517, Σ 1639, and Σ I 21

We’re back once again in northwestern Coma Bernices to finish looking at the double and multiple stars in the Coma Cluster. The last time out we covered the north half of the cluster (if you missed part one, you can get there by clicking on this link), so this time we’ll wander among the stars in the southern half.

If you need to get oriented, here’s an overview of where we’re headed:

You’ll find Coma Bernices wedged between the eastern edge of Leo and western edge of Boötes.   The Coma Cluster sits just south of Gamma (γ) Comae Bernices. (Stellarium screen image with labels added, click for a larger view).

You’ll find Coma Bernices wedged between the eastern edge of Leo and western edge of Boötes. The Coma Cluster sits just south of Gamma (γ) Comae Bernices. (Stellarium screen image with labels added, click for a larger view).

Once you locate the cluster, which is easily seen under dark skies as a ghostly scattering of star dust, point your telescope at Gamma (γ) Com and then pan a couple of degrees south:

The Coma Cluster also goes by two other designations, Collinder 256 (Cr 256) and Melotte 111 (Mel 111).   We’re headed for the south half of the cluster, but we’ll start by centering 14 and 16 Com in our finder. (Stellarium screen image with labels added, click to enlarge the chart).

The Coma Cluster also goes by two other designations, Collinder 256 (Cr 256) and Melotte 111 (Mel 111). We’re headed for the south half of the cluster, but we’ll start by centering 14 and 16 Com in our finder. (Stellarium screen image with labels added, click to enlarge the chart).

Once you’ve got 14 and 16 Com positioned in the center of your finder field, look one degree southwest of 16 Com to the white glow of 5.17 magnitude 13 Com. From there move half of a degree southwest (a bit more west than south this time) to 4.81 magnitude 12 Com, also known as SHJ 143.

SHJ 143 (12 Com)      HIP: 59468   SAO: 82273
RA: 12h 22.5m   Dec: +25° 51’
Identifier          Magnitudes       Separation       Position Angle      WDS
SHJ 143   AB:  4.86, 11.80           36.70”                   57°              2012
H V 121    AC:  4.86,  8.90           59.00”                 168°              2012
ARN 6      AD:  4.86, 10.10         213.10”                 132°              2012
SMR 57    DE: 10.10,14.30           12.80”                 167°              2013
Distance: 775 Light Years
Spectral Classifications:  “A” is F6, “B” is F8, “C” is F5, “E” is K5

 I found the primary to be a beautiful gold, which fits somewhat closely with its F6 spectral classification (yellow-white leaning toward yellow), “B” was very hard to see in the primarial glare, and “C” and “D” stood out clearly. 14.30 magnitude “E” was visually out of reach for my six inch lens. (East & west reversed to match the refractor view, click on the sketch for a better image).

I found the primary to be a beautiful gold, which fits somewhat closely with its F6 spectral classification (yellow-white leaning toward yellow), “B” was very hard to see in the primarial glare, and “C” and “D” stood out clearly. 14.30 magnitude “E” was visually out of reach for my six inch lens. (East & west reversed to match the refractor view, click on the sketch for a better image).

To give credit where credit is due, we need to start with Sir William Herschel who was here first on January 1st, 1783, with an observation (scroll down to the sixth title) of what is now the AC pair:

Wm. Herschle on 12 Com

One of the odd things I noticed about his observation was although he provided a very precise measurement of separation, 58.55”, his position angle was only an estimate, although a pretty good one since his “77° s. following” works out to our present day 167°. However, as we’re about to see, it turns out his estimated position angle was the more accurate of the two numbers.

When Sirs John Herschel and James South looked at the same pair on the evening of May 21st, 1821, they came up with a similar position angle, 168.47°, but a considerably different separation, 65.950”, as you can see in this page from their 1824 catalog (scroll down to last title):

Herschel-South on HJ 143

We have to leap ahead to 1904 to discover the Herschel/South separation is the more accurate number, as this excerpt from S.W. Burnham’s 1906 catalog shows:

Burnham on 12 Com

Burnham was the first to detect what is now “B”, which he measured at 54.1° and 35.00”. You may have also noticed the William Herschel catalog number he lists for the AC pair is incorrect, which is one of the rare errors in Burnham’s many publications.

The WDS doesn’t list the AC pair with the H V 121 identifier, instead using SHJ 143, presumably because the Herschel-South measure was more accurate than Sir William’s. On the other hand, Burnham’s prefix of “Bu” hasn’t been assigned to the AB pair, which should be the case if the same logic was applied.

Click to enlarge.

Click to enlarge.

But since splitting hairs can be as intriguing as splitting stars, I stumbled across what appears to be another error, or at least a puzzling problem.   Brian Mason at the USNO (home of the Washington Double Star Catalog, or WDS) was kind enough to send me the text file for SHJ 121, which includes forty-eight measurements of the AC pair from 1783 through 2012 (see insert at right).

All of them, with the exception of William Herschel’s 1783 measure (58.91″) and the most recent 2012 measure (58.97″), show the AC pair with a separation varying between 63.6” (2009.14) and 66.8” (2011.323). The vast majority of the forty-eight observations are in the 65 arc second plus range – in fact, when the 1783 and the most recent 2012 measures are excluded, the remaining forty-six average out to 65.34”. For some reason, three of the last five measures listed in the WDS are particularly erratic: 63.6” (2009.14), 66.8” (2011.323), and 58.97” (2012.414). So in that context, maybe Sir William Herschel’s separation error should be forgiven. The position angle, on the other hand, has been consistently in the 167 degree range all that time.

At any rate, it would appear there’s been very little change in the AC pair, which isn’t surprising since its proper motion is minimal. In fact, one odd thing I noticed about the multiple stars we’re going to look at on this tour is the proper motion of all of them is relatively small, which is quite a contrast to what we saw for the three stars covered in the northern half of the Coma Cluster in part one.

Now if you go back to your finder while SHJ 143 is centered and look southwest once again (here’s our last chart), you’ll see the weak glimmer of 8.06 magnitude HIP 60233 just twenty arc minutes away. Center it your finder and you’ll find the even weaker ninth magnitude light of HJ 517 five arc minutes to the northwest – and you’ll have to sit very still to see the faint 12.50 magnitude secondary.

HJ 517          HIP: 60206   SAO: 82256
RA: 12h 20.8m   Dec: +25° 46’
Magnitudes: 9.09, 12.50
Separation:  20”
Position Angle: 239° (WDS 2001)
Distance: 242 Light Years
Spectral Classification: “A” is F8
Note: Optical pair

Hmmm – look closely or you’ll miss this one! Note that HIP 60233/SAO 82261 makes a handy reference point for locating HJ 517. (East & west reversed again, click on the sketch to see the secondary more easily).

Hmmm – look closely or you’ll miss this one! Note that HIP 60233/SAO 82261 makes a handy reference point for locating HJ 517. (East & west reversed again, click on the sketch to see the secondary more easily).

Like a lot of Sir John Herschel’s discoveries (1827 for this one), this is a faint pair with a very hard to see secondary. I needed averted vision to catch my first glimpse of it, but after that initial glimpse, it flickered in and out of view with direct vision. As you can see, the field is rather sparse and colorless. Apart from the eighth magnitude glow of HIP 60233, there’s nothing here to write home about.

Now let’s go back and center SHJ 143/12 Com in the finder and locate Σ 1639. If you look at our last chart closely, you’ll see 12 Com and 13 Com form a triangle with 6.47 magnitude Σ 1639. It shines thirty arc minutes southeast of 12 Com/SHJ 143 and thirty-one arc minutes south of 13 Com.

Σ 1639         HIP: 60525   SAO: 82293
RA: 12h 24.4m   Dec: + 25° 35’
Magnitudes   AB: 6.74, 7.83      AC: 6.74, 11.50
Separations   AB: 1.82”             AC: 91.60”
Position Angles  AB: 323.2° (WDS 2014)   AC: 160° (WDS 2009)
Distance: 319 Light Years
Spectral Classifications: “A” is A7, “B” is F4
Note: “A” and “B” are a binary pair

The real test here is splitting the AB pair, both of which appeared white to me. Although dim at a magnitude of 11.50, “C” is far enough away to stand out clearly. (East & west reversed once more, click on the sketch to improve the view).

The real test here is splitting the AB pair, both of which appeared white to me. Although dim at a magnitude of 11.50, “C” is far enough away to stand out clearly. (East & west reversed once more, click on the sketch to improve the view).

With poor seeing once again ruling the heavens, it took a determined effort to mentally hold the AB pair still for long enough to detect a hint of duplicity. After several minutes of serious 127x staring, an elongation eventually became evident. I coaxed both stars into view at 203x with a 7.5mm Celestron Plössl, but their energetic up/down/sideways dance made it impossible to see any black space between them.

Click on the image to enlarge it.

Click on the image to enlarge it.

The primary and secondary are a true binary pair with an orbital period which has never been quite pinned down. In his 1906 catalog, S. W. Burnham estimated it to be in excess of four hundred years and mentions Thomas Lewis estimated it at 180 years. The WDS data (which can be seen here) shows two numbers for the orbital period: 575.44 years is the number shown with the orbital chart, and 678 years is shown if you scroll further down the page to the note below the second chart.

There is one thing about the orbital data which is definite: the separation of the pair will gradually increase for about another twenty or thirty years, although not by much – 1.925” is the separation shown for the last year listed (2030) in the table to the left of that chart. In the past, the primary and secondary have been as close as .20” (1889 in Burnham’s data at the right), and in fact was probably less than that in 1892 when Burnham shows he was unable to separate them with the 36 inch refractor at Lick Observatory.

Back to the finder now as we head for out last star (here’s our chart again).  Sitting in the middle of the east leg of the triangle formed by 12 Com/13Com/Σ 1639 is 6.71 magnitude HIP 60490.   A line drawn from 12 Com/SHJ 143 directly through HIP 60490 will lead you to 6.67 magnitude HIP 60797 (69 arc minutes east of 12 Com/SHJ 143), and another seventeen arc minute hop in the same direction will land you on our last target, 5.32 magnitude 17 Com, aka Σ I 21, aka STFA 21.

Σ I 21  (17 Com)  (AB is also S 638)        HIP:60904   SAO: 82330
RA: 12h 28.9m   Dec: +25° 55’
Identifier         Magnitudes        Separation       Position Angle       WDS
STFA 21   AB: 5.23,  6.64           144.90”                250°               2012
Bu 1080   AD: 5.23, 13.70           324.20”                269°               2001
SLE 898   AE: 5.23, 12.10           447.50”                270°               2001
SLE 898   AF: 5.23, 12.70           125.90”                146°               2001
Bu 1080   BC: 6.64, 13.70               1.50”                175°               2009
Bu 1080   BD: 6.64, 13.70            193.00”                284°               2001
Distance: 270 Light Years
Spectral Classification:  “A” is A0

All of the components can be seen in my sketch except for “C”, which was well beyond my reach because of the 7.06 magnitudes of difference between it and “B”. Both “A” and “B” were white, as was HIP 60797. (East & west reversed, click on the sketch for a much better view).

All of the components can be seen in my sketch except for “C”, which was well beyond my reach because of the 7.06 magnitudes of difference between it and “B”. Both “A” and “B” were white, as was HIP 60797. (East & west reversed, click on the sketch for a much better view).

When I first looked at this system I had a tough time prying 12.7 magnitude “F” out of the glare, so I returned three nights later for another look. Surprisingly I saw it immediately at 84x with an 18mm Radian, although it flickered in and out of sight after the first sighting. When I moved up to 118x with a 14mm Radian, it pretty much disappeared into the primarial glare because of an over-abundance of moisture in the air.

One of the things I noticed quickly as I located the components of Σ I 21 was that “D” appeared brighter than the 13.70 magnitude listed for it in the WDS. The UCAC4 catalog shows “D” (UCAC4-580-047409) at a magnitude of 11.50, which matches closely with what I saw. I also thought “E” was a bit brighter than the 12.10 magnitude shown in the WDS, but the UCAC4 catalog has it (UCAC4-580-047416) at a magnitude of 12.08.

The first date of observation for the AB pair in the WDS is listed as 1836, but Burnham’s 1900 catalog of double stars (A General Catalogue of 1290 Double Stars Discovered from 1871 to 1899) refers to it as S 638, which quickly lured me to Sir James South’s 1826 catalog. And sure enough, he made two observations of the AB pair in March of 1825, coming up with a final PA and separation of 251° 13’ and 144.436”.

South on SFTA 21 (S 638)

I was also curious about what Burnham had used to cut through the seven magnitudes of difference between 6.64 magnitude “B” and 13.70 magnitude “C”, and not surprisingly it was that great optical equalizer, the 36 inch Lick refractor (click on the arrow at the right side of the photo — there are four different views of the refractor!).

Burnham on STFA 21

There appears to be some significant motion in one of those two stars since the two similar measures of BC shown in the excerpt above (the first by Burnham, the second by R.G. Aitken) differ in separation, and especially in position angle, from the 2009 data in the WDS.

That’s it for the Coma Cluster, which you’ll have to catch quickly since it’s now sinking into the western sky. Next time out we’ll wander east to Hercules and take advantage of some rare good seeing to pry apart two doubles that have eluded me for the past year.

Clear Skies until then! :cool:

Caught in the Coma Cluster, Part 1: Σ 1633, Σ 1643, and Σ 1651

Many is the night I’ve cast a curious glance at that faint cluster of jewel-like stars that follow Leo through the heavens, thinking I should point a telescope into it and see what kind of double star life lurks within. With the aid of an eleven inch SCT I combed through the cluster several years ago in search of the many galaxies that lurk at dim magnitudes beyond the reach of my six inch refractor, but the large SCT was meant for deep sky exploration, not double stars, so I zipped right past them – if I noticed them at all – as I peered millions of light years into the past.

But times change – as well as telescopes – and I eventually abandoned the eleven inch SCT when I discovered the double star world that springs to life in small and medium sized refractors. Other than peering into the past in terms of light years, I’ve never looked back to regret selling the SCT since on most nights it was way too much aperture for the typical seeing conditions at my location. But I always intended to return to the Coma Cluster and satisfy my double star curiosity, and that’s exactly what I’m going to do now.

The Coma Cluster is the faint collection of shimmering stars located immediately south of Gamma (γ) Comae Bernices. If you have trouble picking it out because of overly bright skies, point a pair of binoculars about two-thirds of the way between Denebola (Beta/β Leonis) and Cor Coroli (Alpha/α Canum Venaticorum) and it will spring into life. (Stellarium screen image with labels added, click on the chart to enlarge it).

The Coma Cluster is the faint collection of shimmering stars located immediately south of Gamma (γ) Comae Bernices. If you have trouble picking it out because of overly bright skies, point a pair of binoculars about half way between Denebola (Beta/β Leonis) and Cor Coroli (Alpha/α Canum Venaticorum) and prepare to be dazzled by the light. (Stellarium screen image with labels added, click on the chart to enlarge it).

The Coma Cluster goes by two designations, Collinder 256 and Melotte 111, and is generally considered to be about four to five degrees in diameter. It was described by Garrett P. Servis as “gossamers spangled with dewdrops”, a description I’m not about to try to improve on.  (Thanks to the late Walter Scott Houston for that reference — scroll down to the bottom of this page for his account of the Coma Cluster, along with a pretty good photograph).  Latest estimates of the cluster distance put it at about 280 to 288 light years from us.

Gamma (γ) Comae Bernices is located at the top center of this chart, which will help you to get oriented.  All of the stars we’re going to look at are sprawled out south of Gamma γ). (Stellarium screen image with labels added, click on the chart for a larger view).

Gamma (γ) Comae Bernices is located at the top center of this chart, which will help you to get oriented.  The diameter of the circle is about 3.5 degrees, so the entire cluster will fit into the typical five degree field of an 8×50 finder.  All of the stars we’re going to look at are sprawled out south of Gamma (γ).  (Stellarium screen image with labels added, click on the chart for a larger view).

Surprisingly, the seven multiple stars I looked at in the Coma Cluster are conveniently separated into two groups. We’ll cover the north half of the cluster in this post – which means Σ 1633, Σ 1643, and Σ 1651 – and tackle the southern half in the next post.

The best place to start is at Gamma (γ) Comae Bernices, which is located in the northwest corner of the constellation, as shown in the first chart above.   Once you locate it, center it in your finder and one degree south of it you’ll see 4.92 magnitude 14 Com, with 4.98 magnitude 16 Com half a degree to its south.  We’re going to start with Σ 1633, which lies almost a degree and a half west of 14 Com.  8.47 magnitude HIP 60364, which is about two-thirds of the distance to Σ 1633, can be used as a convenient stepping stone.

Σ 1633 (H N 31)  (SHJ 141)  55 Com
HIP: 60197   SAO: 82254
RA: 12h 20.7m   Dec: +27° 03’
Magnitudes: 7.04, 7.13
Separation:  8.9”
Position Angle: 245°  (WDS 2013)
Distance: 301 Light Years
Spectral Classifications: F3, F3

A classic case of a pair of headlights coming right at you, so duck! Both stars appeared perfectly white to me. (East & west reversed to match the refractor view, click on the sketch for a much better image).

A classic case of a pair of headlights coming right at you, so duck! Both stars appeared perfectly white to me. (East & west reversed to match the refractor view, click on the sketch for a much better image).

As you can tell by the first line of the data above, this pair of stars has had a lot visitors. Sir William Herschel was here first, on April 6th, 1785 (p. 170 of this link), F.G.W. Struve in 1820 and 1831 (p. 329 of Lewis book), but it was the observations by Sirs John Herschel and James South in 1821 and 1823 which are the most interesting (source — scroll to bottom of page).

Click to enlarge.

Click to enlarge.

Their observations (shown at the right) show a frustrating effort to wrestle consistent measures from the pair of stars on three separate nights. And if you look at their position angles for each of the three dates shown, you can see they had a difficult time deciding which of the two stars were brightest.

On March 14th, 1821, the average of their five position angles is presented as one number with both sp (south preceding) and nf (north following) added to it.  The 23° 46’ sp, which refers to what is now “A”, translates to our present day 246° 14’; and 23° 46’ nf, for what is now “B”, is exactly 180° less (66° 14’).  You can see they settled on the dimmer of the two stars for their April 10th, 1823, position angle (23° 12’ nf is 66° 48’), but nine days later they measured their position angles from what is actually the brighter of the two stars, 24° 13’ sp (245° 47’). I didn’t have any problem determining which of the two stars was brightest, but I had the benefit of using a six inch refractor, whereas Herschel and South were using a 3.8 inch refractor.

They also had problems measuring the separations of the two stars, with averages of 9.646”, 10.007”, and 8.843”. You can read their comments on the influence of the seeing conditions at the bottom of the page, which apparently were pretty darn good on the second night of their observations. At least once this year I would love to see the night of “steadiness and exact definition of the stars” they describe.

Surprisingly, their measure which is closest to that of the current WDS figures didn’t come on the night of the best seeing.  And there’s really no reason to suspect much change in the separation because these two stars are locked in a tight physical relationship defined by proper motion. In fact, both “A” and “B” have the same motion, +009 -120 (.009”/year east and .120”/year south), which is shown clearly in this Simbad chart:

Labels added for clarity, click on the chart to enlarge it.

Labels added for clarity, click on the chart to enlarge it.

Savor the comparatively wide separation of these two stars for a moment . . . . . . . . . . . because the next two selections get progressively tougher.

Let’s move the scope back to 14 and 16 Comae Bernices now.  A careful look in an 8×50 finder will reveal Σ 1643 sitting midway between 14 and 16 Com, or if that doesn’t work for you, place those two stars in your eyepiece so they’re at opposites sides of the field of view. (Here’s our last chart again).

And then look closely – very closely.

Σ 1643  (C is LEP 54)     HIP: 60759   SAO: 82315
RA: 12h 27.2m   Dec: 27° 01’
Magnitudes   AB: 9.03, 9.45     AC: 9.03, 14.78
Separations   AB: 2.7”              AC: 221.70”
Position Angles   AB: 4.1° (WDS 2014)     AC: 261 (WDS 2001)
Distance: 90 Light Years
Spectral Classifications:  “A” is K2, “B” is K4, “C” is M 4.5
Notes: “C” is a variable, V* CX Com

If you look carefully at the east-center of the field of view, you should see two faint and very close stars, provided you have enough magnification. I could barely separate them at 84x in an 18mm Radian, so I increased the magnification to 118x with a 14mm Radian. Even then, they were still tough to separate visually. The 14.78 magnitude “C” component is hiding west of the AB pair, but it was well beyond the reach of my six inch refractor. (East & west reversed again, click on the sketch to improve the view).

If you look carefully at the east-center of the field of view, you should see two faint and very close stars, provided you have enough magnification. I could barely separate them at 84x in an 18mm Radian, so I increased the magnification to 118x with a 14mm Radian. Even then, they were still tough to separate visually. The 14.78 magnitude “C” component is hiding southwest of the AB pair, but it was well beyond the reach of my six inch refractor. (East & west reversed again, click on the sketch to improve the view).

And for those who prefer a less cluttered view, here’s an unlabeled version of the same sketch:

Click on the sketch to enlarge it.

Click on the sketch to enlarge it.

One of the things you’ll probably notice in the sketch – and which you definitely notice at the eyepiece — is the Σ 1643 pair is easy to overlook because of the dominating fifth magnitude white brilliance of 14 Com (mag 4.92, spectral class F0) and 16 Com (mag 4.98, spectral class A4).  And sitting two and half arc minutes west of 16 Com is an innocent looking white star, LDS 1308 (magnitudes of 8.8 and 18.3, 51.1”, 214°, WDS 2004), which hides a secondary well out of our visual reach.

The AB pair of Σ 1643 is performing a very slow dance around each other, which is estimated by WDS orbital charts at either 549 years or 1628 years (those charts can be seen here if you scroll down to the middle of the view). Each of the charts show the two stars are actually about as far apart as they can be — don’t rush, though, you’ve got a few hundred years before they get noticeably closer.

And both stars also have significantly high rates of proper motion, which is shown in this Simbad chart:

Labels added for clarification, click on the chart for a larger view.

Labels added for clarification, click on the chart for a larger view.

Simbad combines the AB pair into one arrow on that chart, since the two are orbitally attached. It shows the proper motion of the pair at +094 -249 (.094”/year east, .249”/year south), but the WDS lists slightly different numbers for each of the components (A at +096 -229, B at +085 -240). You can also see that 14.78 magnitude “C” is moving parallel to the AB pair at +089 -250 (Simbad and WDS numbers).

Now let’s slide one degree east to 8.65 magnitude Σ 1651, which is shadowed to its north by the slightly brighter HIP 61118 (7.5 magnitude).  Here’s that last chart again.

Σ 1651  (88 Com)      No HIP Number   SAO: 82357
RA: 12h 31.7m   Dec: 27° 01’
Magnitudes: 8.56, 10.20 (from Simbad)
Separation:  7”
Position Angle: 214° (WDS 2012)
Distance: 148 Light Years
Spectral Classification: “A” is G1, “B” is K1

Now you REALLY have to look closely this time. Even though this pair is wider, the 1.56 magnitudes of difference makes a HUGE difference. The primary was white, and the secondary was barely visible without averted vision. (East & west reversed again, click on the sketch to get a much better glimpse of the faint secondary).

Now you REALLY have to look closely this time. Even though this pair is wider than our previous pair, the 1.56 magnitudes of difference makes a HUGE difference when compared with the equal magnitudes of that one. The primary was white, and the secondary was barely visible without averted vision. (East & west reversed again, click on the sketch to get a much better glimpse of the faint secondary).

Shown in the sketch just three and half arc minutes northwest of the Σ 1651 pair is the same 7.5 magnitude HIP 61118 we saw in the finder earlier.  I’m surprised one of the late eighteenth/early nineteenth double star observers didn’t include it in one of their observations, if for no other reason than to use it as a reference point for the proper motion of Σ 1651. Simbad places HIP 61118 at 465 light years from earth, so it’s obviously not related to the Σ 1651 pair, which are located 148 light years from us. I didn’t see any color in that star, but with a spectral class of K3 there should have been some reddish/orange visible in it.

The two stars of Σ 1651 aren’t orbitally attached, but they do appear to be related physically by proper motion.  And again, a Simbad chart illustrates that very clearly:

Labels added for clarity, click on the chart for a larger view.

Labels added for clarity, click on the chart for a larger view.

Click to enlarge.

Click to enlarge.

The proper motions illustrated on the chart above are +027 +008 [.027”/year east, and .008”/year north] for “A”, and +026 +006 for “B”. Shown at the right is an excerpt from Lewis’ book on Struve’s double stars, which shows quite a bit of consistency when the position angle of 1858 is excluded. S.W. Burnham (p. 608 of this book) measured the pair at 217.4° and 6.83” in 1905, resulting in an impression of very little change, if any, over the seventy-five year period of the data.

I also found WDS data showing the PA in 1982 was measured at 215°, in 1991 at 214°, and in 2004 again at 214°. Separation for that same period was measured at 7” (1982), 6.9” (1991), and 6.9” (2004). Based on the proper motion numbers, you might expect a very slight change in relative positions of the stars, which may well be what the slight change in PA and separation show. On the other hand, the changes are so slight, especially the separation, they could simply be statistical fluctuations.

And that’s it for the north part of the Coma Cluster.   Coming up next is a tour of four stars lurking in the southern half.

Until then, Clear Skies! :cool:

Untangling the Knots in Bernice’s Hair: 32 Com, Σ 1685, and Σ 1686

Wedged between Boötes and Leo, Coma Bernices is one of those dim and non-descript constellations that gets completely lost in a light-polluted sky. But even when the background of the celestial vault is dark, the only notable characteristic of this collection of stars is a faint and fuzzy open cluster appearance emanating from its northwest corner.  Consequently, navigation via star hopping can be a treacherous experience if you make a wrong turn. Fortunately for this tour, I found three distinctive multiple stars that not only are within four degrees of each other, but are also located almost directly in line with one another.  All you have to do to get started is throw a rope around Alpha (α) Comae Bernices and then fling it out to the west a few degrees.

First, though, you have to find Alpha (α) Com, which requires a sharp eye and a reasonably dark sky.

I got there by starting at Porrima (Gamma/γ Virginis) in northern Virgo and working my way up to Delta (δ) and then to Epsilon (ε). The line formed by Delta (δ) and Epsilon (ε) Virginis points almost directly at Alpha (α) Com, which lies a short seven degrees away. Another way is to follow the line that runs through Arcturus (Alpha/α Boötis) and Eta (η) Boötis. Extending it for ten and half degrees it leads you directly to Alpha (α) Comae Bernices. (Stellarium screen image with labels added, click on the chart to enlarge it).

I got there by starting at Porrima (Gamma/γ Virginis) in northern Virgo and working my way up to Delta (δ) and then to Epsilon (ε). The line formed by Delta (δ) and Epsilon (ε) Virginis points almost directly at Alpha (α) Com, which lies a short seven degrees away. Another way is to follow the line that runs through Arcturus (Alpha/α Boötis) and Eta (η) Boötis. Extending it for ten and half degrees it leads you directly to Alpha (α) Comae Bernices. (Stellarium screen image with labels added, click on the chart to enlarge it).

Once you’ve groped your way in the dark to Alpha (α) Com, turn your attention to the west and follow me to our first stop, 32 Com:

From 4.32 magnitude Alpha (α) Com make a short two and a half degree hop due west and slightly south to 4.79 magnitude 36 Com. Another one and a half degrees further west, with a slightly more inclined lean to the south will get you to the orange and white starlight of 32 and 33 Com.   You’ll find them sitting midway between 36 Com and 5.12 magnitude 27 Com. (Stellarium screen image with labels added, click for a larger version).

From 4.32 magnitude Alpha (α) Com make a short two and a half degree hop due west and slightly south to 4.79 magnitude 36 Com. Another one and a half degrees further west, with a slightly more inclined lean to the south will get you to the orange and white starlight of 32 and 33 Com. You’ll find them sitting midway between 36 Com and 5.12 magnitude 27 Com. (Stellarium screen image with labels added, click for a larger version).

32 Com  (STFA 23)        HIP: 62807   SAO: 100309
RA: 12h 52.2m  Dec: +17° 04
Magnitudes    AB: 6.50, 6.99   AC: 6.50, 8.95
Separations   AB: 195.90”       AC: 905.10”
Position Angles  AB: 51° (WDS 2011)   AC: 262° (WDS 2001)
Distance: 1833 Light Years
Spectral Classifications: “A” is M0, “B” is F8
Note: “B” is 33 Com

This is a pleasantly tinted wide triple star that would work well in a 60mm refractor, so my 9.25 inch SCT view was way more aperture than you need for it.  Even at that aperture, though, there weren’t a lot of stars to be seen in the field of view.

The orange/gold primary is at the center of the sketch, the slightly weaker secondary is parked above and to its right (northeast), and the considerably weaker and more distant “C” component lies at the west edge of the field of view. Lying almost directly in line with the AB pairing to the southwest is a pair of faint stars (the first is 13th magnitude, the second 12th) which add a little extra visual appeal to the scene.   (East and west reversed to match the SCT view, click on the sketch for a much better version).

The orange/gold primary is at the center of the sketch, the slightly weaker secondary is parked above and to its right (northeast), and the considerably weaker and more distant “C” component lies at the west edge of the field of view. Lying almost directly in line with the AB pairing to the southwest is a pair of faint stars (the first is 13th magnitude, the second 12th) which add a little extra visual appeal to the scene. (East and west reversed to match the SCT view, click on the sketch for a much better version).

You’ll notice the “C” component is waaaaay out there.  The 905.10” of separation for it in the WDS translates to a distant 15.085 arc minutes, which meant I needed a wide field of view to catch it in the same eyepiece view with the AB pair.  My seldom-used 40mm Celestron Plössl was barely enough to snare the 8.95 magnitude star.

The wide separation of the three stars of 32 Com raises a question as to what kind of physical relation exists among them. Considering the rather distant 1833 light years of the primary, you can pretty much rule out any kind of orbital relationship between the three stars because visually they’re too far apart. On the other hand, it’s always possible another kind of physical relationship exists. The best way to get a feel for that is to look at their proper motions, and fortunately the data for all three components is listed in the WDS:

Proper motion of A: +002 -005  (.002” east per year, .005” south/year)
Proper motion of B: +038 -036  (.038” east per year, .036” south/year)
Proper motion of C:  -035 -006  (.025” west per year, .006” south/year)

Pictorially, those movements look like this on a Simbad plot:

Click on the image to enlarge it.

If you look closely at the red mark which is 32 Com, you can see an indication of southeasterly movement, which is the “B” component.  (Click on the image to enlarge it.  NOTE: east is on the left in this view).

So what the WDS data and the Simbad plot tell us is there’s no relation whatever between the three stars. As to what led F.G.W. Struve to measure the AB pair in 1836, I have no idea since I’ve unsuccessfully turned the internet upside down numerous times trying to locate his 1837 catalog, Stellarum duplicium et multiplicium mensurae micrometricae per magnum Fraunhoferi tubum annis a 1824 ad 1837 in specula Dorpatensi institutae.  What I did find (in the WDS) was his initial data on the AB pair, 194.7” and 49 degrees, showing very little change in the almost 180 years since that observation was made. As for AC, its first measurement was made in 1875, 898.1” and 262 degrees, which again shows very little change.

We’ll move south now and take a look at Σ 1686, which lies two degrees south of 32 Com. You can use 6.25 magnitude HIP 62825 as a stepping stone since it conveniently lies halfway between 32 Com and Σ 1686.   (Here’s our last chart again).

Σ 1686  (SHJ 155)     HIP: 62852   SAO: 100315
RA: 12h 53.0m   Dec: +15° 02
Magnitudes: 8.58, 8.72
Separation:  5.7”
Position Angle: 186° (WDS 2013)
Distance: 482 Light Years
Spectral Classification: F5, F8

Two lovely white dots of light! (East & west reversed, click on the sketch for a better look).

Two lovely white dots of light! (East & west reversed, click for a better view).

As you can see, there’s a peculiar absence of background stars in this view. That’s because Coma Bernices lies well outside the plane of the Milky Way, which means we’re looking deep into inter-galactic space. In fact, it’s that particular trait that makes Come Bernices such a happy hunting ground for galaxies.

Even though this pair of stars carries F.G.W. Struve’s designation, their first measurement was made by Sirs James South and John Herschel on June 6th, 1823.

 Click on the image to enlarge it.

Click on the image to enlarge it.

Click to enlarge.

Click to enlarge.

The separation they measured is too wide, which James South calls attention to in the remark he added at the bottom of the observation.   Their position angle, which refers to both south preceding (sp) and north following (nf), is vague because they weren’t sure which of the two stars was the brightest. The correct PA is 79° 53’ sp (190° 07’), which is also noticeably off by a few degrees when compared with the data in the excerpt from Thomas Lewis’s Measures of the Double Stars Contained in the Mensurae Micrometricae of F.G.W. Struve (shown at the right).  That data shows virtually no change at all in the position angles and separations of the two stars between 1829 and 1897, and in fact, most of the numbers aren’t all that different from the 2013 WDS figures.

Let’s go back to 32 Com now and then hop north two degrees to Σ 1685, which you’ll find wedged between 7.05 magnitude HIP 62930 and 7.22 magnitude HIP 62724. (Here’s our previous chart again).

Σ 1685  (SHJ 153)  (AB is H IV 58, and also HJL 173)     
HIP: 62783   SAO: 100307
RA: 12h 51.9m   Dec: 19° 10’
Identifier         Magnitudes      Separation      Position Angle       WDS
STF 1685   AB: 7.31, 7.78          15.90”                201°              2012
SHJ 153     AC: 7.31, 8.22        243.10”                328°              2012
SHJ 153     BC: 7.78, 8.22        252.50”                331°              2012
Distance:  “A” is 720 LY, “B” is 481 LY, “C” is 282 LY
Spectral Classification:  “A” is A3m, “B” is F8, “C” is G7

If by some chance you’re approaching Σ 1685 without having been centered on 32 Com, there’s another way to get here, which is best described by the admirable Admiral William H. Smyth:

A neat double star, between Bernice’s Hair, and Virgo’s left wing:  it lies due west of Arcturus, or on its parallel, at the distance of 22°, where a line dropped south from Cor Caroli will intercept it.  A 7 ½, and B 8, both white; other stars in the field, but small and distant.  This object is 58 H IV; and is also formed by Nos. 201 and 202, Hora XII., of the Palermo Catalogue.”  (From The Bedford Catalog, p. 284)

In fact, even William Herschel provided pretty good directions (source):

Wm Herschel on STF 1685The stars he refers to as 42nd and 15th Comae Bernices are Alpha (α) and Gamma (γ) Com, which are included on our first chart.  His comment about being parallel to those stars refers to the alignment of the AB pair of Σ 1685, which is parallel to a line drawn from Alpha (α) to Gamma (γ) Com.

Regardless of how you get there, this is what you’ll see when you arrive:

The AB pair is at the center of this view, and “C” is suspended about fifteen times further away to the northwest (above and to the left). The unrelated 7.22 magnitude HIP 62724, surrounded by eleventh and thirteenth magnitude stars, adds a little visual spice to the scene over in the far west corner of the view. The only color to be seen here was white. (East & west reversed, click on the sketch for a much better view).

The AB pair is at the center of this view, and “C” is suspended about fifteen times further away to the northwest (above and to the left). The unrelated 7.22 magnitude HIP 62724, surrounded by eleventh and thirteenth magnitude stars, provides an interesting contrast to the primary/secondary pairing. The only color to be seen here was white. (East & west reversed, click on the sketch for a much better view).

Again, even though F.G.W. Struve’s name is associated with this multiple star, both Sir William Herschel and the Hershel/South duo arrived on the scene a few years ahead of him. Admiral Smyth was kind enough to compile a list of the dates and data from all of those observations, which I’ve summarized below. The Admiral accurately noted there was little difference between the various measures: “A comparison of my own with the following measures, afford presumptive proof of fixity.”

Wm. Herschel             Pos. 202° 03’      Dist. 15”.86        Ep. 1782.30
H. and S.                            202° 11’              16”.96              1823.41
Σ..                                      200° 48’              15”.82              1829.87
Wm. Smyth                        201°.40’              15”.90              1831.39
Wm. Smyth                        201°.90”              16”.20              1838.28

Actually, that “fixity” is a bit deceiving, but before we get to that, we’ll take a look at John Herschel and James South’s observation, which includes the “C” component not included by William Herschel (source):

Click on the image to enlarge it.

Click on the image to enlarge it.

They only made one measure of the AC pair, which is the “3rd star” referred to below their measures of the AB pair. Their 59° 23’ np works out to 329° 23’, and their 4’ 9”.666 equals 249.666 when converted into arc seconds, both of which are remarkably close to the 2012 WDS data of 328° and 243.10”. They also include a reference to a fourth star, which they locate at 4° 0’ sp (266.0°) and 10’ 31.644”. That star is HIP 62724, which is shown at the left edge of the field in my sketch above.

That takes us back to Admiral Smyth’s remark about “fixity”, which later astronomical observations would probably term “relative fixity.” As it turns out, there’s quite a bit of motion within this grouping of stars, which looks like this on Simbad’s plot of the motion:

Click to enlarge the chart.

Click to enlarge the chart.

Another way of peering into what’s taking place here is to look at the actual proper motion numbers for the stars labeled in the plot (all the data is from Simbad, which varies slightly from the WDS data):

Σ 1685 A:                 -079 +006  (.079” per year west, .006” per year north)
Σ 1685 B:                 -092 +007  (.092” per year west, .007” per year north)
Σ 1685 C:                +017 +012  (.017” per year east, . 012” per year north)
HIP 62724                -145 +019  (.145” per year west, .019” per year north)
TYC 1452-724-1        -068 +045  (.068” per year west, .045” per year north)
TYC 1452-588-1        -066  -023  (.066” per year west, .023” per year south)

And now let’s return to my sketch of Σ 1685 and add labels:

Click for a larger image!

Click for a larger image!

Now if you compare my sketch side-by side with the Simbad chart (click here to open it an adjacent window), you’ll quickly realize something’s not quite right. That’s because east and west are reversed in my sketch, while the Simbad plot is a correct (erect) image view.  So you can either view this as an opportunity to stretch you mental agility by horizontally flipping either image in your mind, or if that proves to be too confusing, here’s a mirror-image version of the Simbad plot, which matches the labeled sketch above:

Click to enlarge the chart.

Click to enlarge the chart.

You can see that not only are the “A” and “B” components of Σ 1685 marching slowly west (virtually in tandem), but HIP 62724 is also moving in the same direction, although as the both the length of the arrow on the chart and the proper motion numbers above show, its speed is greater. On the other hand, the two stars with the TYC designations, 11.1 magnitude TYC 1452-074-1 and 10.9 magnitude TYC 1452-588-1, seem to be intent on marching to the beat of their own drummers.

There’s also an interesting range of distances among these stars:

Σ 1685 A:     720 Light Years
Σ 1685 B:     481 Light Years
Σ 1685 C:     282 Light Years
HIP 62724:   221 Light Years.

If those distances are correct (all of those are based on the parallaxes found in Simbad), not even the “A” and “B” components of Σ 1685 are related. The “C” component is already at such a visual distance from the AB pair that any type of gravitational influence is unlikely.

So that little scenic trip off the beaten path provides an interesting look into an aspect of double stars that is in no way apparent to the telescopically-aided eye. Sometimes it’s interesting to probe just a bit further in order to get a three dimensional image of what would otherwise be invisible.

Next stop – maybe in Coma Bernices, maybe not.  This has been such an uncooperative year from both a clear sky and a seeing standpoint that good nights have been as rare as a long focus refractor at a Dobsonian convention.

 Meanwhile, Clear and Stable Skies —— somewhere!   :cool:

(Actually, I did make it back to Coma Bernices — here’s the first part of a two part post).

Multiple Delights in Canis Minor: Gomeisa (Beta CMi), 14 CMi, and Bu 23

NBWS (Note before we start):  It’s getting a bit late in the year for this part of the sky, so if Canis Minor is lost in the evening’s glare where you are, park this piece for a few months until it returns to a more favorable position.   Time got away from me on this one).

** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** **

Been feelin’ a bit bleary-eyed, lately? Too many late nights under the stars followed by early morning wake up calls from a very impolite and shrill alarm? Well if that’s the case, you might just as well focus those bleary eyes on a star that’s been named in your honor.

Gomeisa, the Beta (β) star of Canis Minor, earned its name from an early Arabic astronomer who apparently kept the same schedule.  It seems Gomeisa is an Arabic phrase meaning “the little bleary-eyed one.”

And it has enough companions that just trying to track all of ‘em down will leave you more than a little bleary-eyed.

Meanwhile, over in the southeast corner of Canis Minor you’ll find another multiple star with a few less companions, but certainly no less challenging.  And hovering near enough to be irresistible is an S.W. Burnham discovery, which of course includes one of his signature visual challenges guaranteed to give your ocular apparatus a whopper of a workout.

First, let’s pin down the location of Gomeisa, which is pure simplicity itself:

Canis Minor, which is located immediately south of Gemini and east of Monceros and Orion, is almost what you might call a two star constellation since the only stars that immediately grab visual attention are Procyon and Gomeisa, the Alpha (α) and Beta (β) of the small dog. (Stellarium screen image with labels added, click to enlarge).

Canis Minor, which is located immediately south of Gemini and east of Monceros and Orion, is almost what you might call a two star constellation since the only stars that immediately grab visual attention are Procyon and Gomeisa, the Alpha (α) and Beta (β) of the small dog. (Stellarium screen image with labels added, click to enlarge).

Gomeisa is easy enough to locate, being a short four degrees northwest of Procyon.  Our second star, 14 Canis Minoris, is almost exactly diagonally opposite Procyon at five and half degrees to the southeast. (Stellarium screen image with labels added, click on the chart to enlarge it).

Gomeisa is easy enough to locate, being a short four degrees northwest of Procyon. Our second star, 14 Canis Minoris, is almost exactly diagonally opposite Procyon at five and half degrees to the southeast. (Stellarium screen image with labels added, click on the chart to enlarge it).

Beta Canis Minoris  (Gomeisa)  (3 CMi)                HIP: 36188   SAO: 115456
RA: 07h 27.2m    Dec:  +08° 17’

Discov# Comp   First   Last     PA    Sep Mag 1 Mag 2
BUP 101    AB   1831   2008   77°    49.0”    2.90   13.0
BUP 101    AC   1879   2008   25°  104.2”    2.90   12.5
BUP 101    AD   1879   2008   76°  131.8”    2.90   12.1
BUP 101    AE   1879   2008 314°  138.3”    2.90   11.6
SLE 571    AF   1984   2008 167°    79.7”    2.90   12.5
SLE 571    AG   1984   2008 177°    83.8”    2.90   13.0
JNN 7    AI   2008   2010 204°      7.5”    3.11   19.8
JNN 7    AJ   2008   2010 353°    10.6”    3.11   17.8
SLE 571    FG   1984   2008 245°    15.1”    12.5   13.0
DAL 41    FH   2000   2008   54°      4.0”    12.5   13.4

Distance: 170 Light Years
Spectral Classifications:  A is B8

What stands out most in this sketch is the glaringly obvious glare of the primary, resulting in what might best be referred to as a partial view of the components.   The primary, in case there’s any doubt, was a very, very bright white.  (East & west reversed to match the refractor view, click on the sketch to get a larger and better view).

What stands out most in this sketch is the glaringly obvious glare of the primary, resulting in what might best be referred to as a partial view of the components. The primary, in case there’s any doubt, was a very, very bright white. (East & west reversed to match the SCT view, click on the sketch to get a larger and better view).

Hiding somewhere in that glare is the secondary (“B”), which was beyond my visible grasp.   For some reason the most concentrated part of the glare was right in the area where “B” should have been. Also out of visual reach was the 13.4 magnitude “H” component, which should have been parked tightly against “F”. And of course, the 19.8 magnitude “I” and the 17.8 magnitude “J” companions were so far out of visual reach they might just as well have been located in an adjacent universe.

Steve Smith was able to capture both the elusive “B” and the faint “H” components in the photograph below, which also gives you some idea of why “B” is so difficult to catch visually.  In fact, there’s another star in his photo located midway between “B” and “D” which also escaped my eyes, that appears to be in the neighborhood of 14th magnitude.  Never under estimate the ability of a good photograph to penetrate the glare that plays havoc with the eyes!

East & west reversed to match the refractor view of the sketch above, click on the image for a larger view.

East & west reversed to match the refractor view of the sketch above, click on the image for a larger view.

Click for a larger view.

Click for a larger view.

The BUP designation in the data above for the “A” through “E” components refers to S.W. Burnham’s 1913 Proper Motion Catalogue (the full title can be seen at the bottom of the image at the right).

You can see Burnham’s data on the AC, AD, and AE components on the adjacent page from his catalog, from which he derived a proper motion of -058 -032 (.058” per year west and .032” per year south).

Those numbers have been revised slightly in the current WDS listing to -052 -038, which isn’t much of a change considering the differences in technology between 1908 and the 2008 WDS readings.

Here’s a look at the Simbad plot of the primary’s proper motion:

Click on the chart to enlarge it.

Click on the chart to enlarge it.

When the primary’s 170 light year distance is taken into account, that seemingly minor amount of movement is actually rather significant. The effect of that motion can be seen by comparing Burnham’s measures with those from the WDS listed at the top of this section.

The WDS shows the first date of observation for the AB pair as 1831, which led me to suspect it was an F.G.W. Struve discovery.   After rummaging around through my accumulation of sources, I discovered the 1831 measures (80 degrees and 35”) were from Admiral William H. Smyth’s entry on Beta (β) CMi in his Bedford Catalog (p. 203 of this edition, which is part of his A Cycle of Celestial Objects). Smyth refers to some measures of other stars in the field by Piazzi, none of which I’ve been able to track down.

We’ve already located 14 Canis Minoris five and half degrees to the southeast of Procyon (here’s that previous chart again), but once we’re there, we’ll need another chart to navigate our way around:

You can see 14 CMi at the lower right of this chart.   When we finish with it, we’ll navigate our way over to Bu 23, which is located off the northeast corner of a rectangle formed by 5.30 magnitude 14 CMi, 4.35 magnitude HIP 39311, 6.75 magnitude HIP 39302, and 6.65 magnitude HIP 38972. (Stellarium screen image with labels added, click for a larger view).

You can see 14 CMi at the lower right of this chart. When we finish with it, we’ll navigate our way over to Bu 23, which is located off the northeast corner of a rectangle formed by 5.30 magnitude 14 CMi, 4.35 magnitude HIP 39311, 6.75 magnitude HIP 39302, and 6.65 magnitude HIP 38972. (Stellarium screen image with labels added, click for a larger view).

14 CMi  (SHJ 87)  (AB is H VI 84)          HIP: 38962    SAO: 116182
RA: 07h 58.3m    Dec: +02° 13’
.       Magnitudes        Separation       Position Angle        WDS
AB:  5.41,   9.36             100.00”                    84°                  2011
AC:  5.41,   9.89             136.90”                  149°                 2011
AD:  5.41, 11.00             114.20”                   281°                1999
BC:  9.36,   9.89             127.90”                  193°                 2004
Distance: 265 Light Years
Spectral Classifications:  “A” is K0, “B” is A0, “C” is K
Notes:  Notable PM of primary (-162 +099)

Even though the primary has a spectral classification of K0 assigned to it, which should put in the reddish-orange to orange category, I could barely detect a weak hint of orange. What really caught my eye was the half circle of faint stars surrounding the southern half of the primary.   (East & west reversed to match the refractor view, click for a better view).

Even though the primary has a spectral classification of K0 assigned to it, which should put in the reddish-orange to orange category, I could barely detect a weak hint of orange. What really caught my eye was the half circle of faint stars surrounding the southern half of the primary. (East & west reversed to match the SCT view, click for a better view).

Despite being assigned a James South-John Herschel prefix (SHJ) by the WDS, it was William Herschel who first discovered 14 CMi as a triple star on February 9th, 1782.   He measured the AB separation at 65.47” with a PA that translates into 63° 26’ under the present system of measuring position angles. He apparently didn’t make any attempt to measure “C”, instead describing it as forming an angle with “A” and “B” and placed it in the south following quadrant (source for excerpt below):

Wm Herschel on 14 CMiForty years later, almost to the day, the duo of James South and John Herschel turned their 3.75” refractor on 14 CMi and, much to their surprise, discovered a very noticeable change in separation and position angle of the AB pair (source for excerpt below, scroll down to the last title).

Click to enlarge.

Click to enlarge.

They took seven measurements, which yielded an average separation of 76.021” and a position angle of 65° 42’.   They also made a single measure of AC at 112.168” and 152° 50’. But it was the change in AB that caught their attention, leading one of them to describe the increase in separation as “very remarkable.”

As we now know, the primary of 14 CMi is the primary culprit for the changes noticed by John Herschel and James South.  Both Simbad and the WDS measure its motion at -162 +099 (.162”/year west, .099”/year north), which is even more remarkable than that of the Gomeisa primary since 14 CMi A is another ninety-five light years further away (265 LY). In fact, it’s not only further away, but the rate of motion is three times faster.   You can get some idea of the difference in rate of motion by comparing the Simbad plot of 14 CMi shown below with that of Gomeisa:

Click on the chart to enlarge.

Click on the chart to enlarge.

Now on to Bu 23, located a very short 1° 21’ to the northeast of 14 CMi. We’ll use our previous chart, but we’ll add distance measurements between the stars to give you a senses of scale:

Stellarium screen image with labels added, click on the chart for a larger version.

Stellarium screen image with labels added, click on the chart for a larger version.

Bu 23         No HIP      SAO: 116264
RA: 08h 02.5m   Dec: +03° 05’
.         Magnitudes        Separation       Position Angle        WDS
AB:    8.27, 12.10                2.70”                    181°                1936
AC:    8.27, 11.27            103.50”                   309°                 2000
CD:  11.27, 12.60             11.40”                    235°                 2000
Distance: ?????
Spectral Classifications:   “A” is K0
Notes: Notable PM of “C” (+105 +069)

Once again, one of S.W. Burnham’s tight, magnitude challenged pairs escaped my vision, so you won’t see “B” on this sketch, although I may have had a glimpse of it at 175x at a position angle of about 175 degrees. The seeing was too poor to surrender any results at a higher magnification, but unlike 14 CMi, this time the K0 spectral classification matched well with the primary’s light orange glow.  (East & west reversed once again to match the SCT view, click on the sketch for a much better version).

Once again, one of S.W. Burnham’s tight, magnitude challenged pairs escaped my vision, so you won’t see “B” on this sketch, although I may have had a glimpse of it at 175x at a position angle of about 175 degrees. The seeing was too poor to surrender any results at a higher magnification, but unlike 14 CMi, this time the K0 spectral classification matched well with the primary’s light orange glow. (East & west reversed once again to match the SCT view, click on the sketch for a much better version).

The CD pair is parked northwest of the primary, and is labeled in the inset in case the two stars escape your attention. Even in this tight seventeen arc minute field of view, HIP 39302’s K2 orange glow managed to sneak into the southwest corner of the field.

Bu 23 strikes me as a strange little discovery for a couple of reasons.  First, the dim magnitudes of the CD pair produce a tenuous appearance in the eyepiece, which gives the two stars a haunting quality.  And second, I’ve also noticed what seems to be a reluctance to fully acknowledge them at the time of discovery.

S. W. Burnham discovered all four of the components on February 2nd, 1872, with his six inch f/15 Clark refractor, but only provided an estimate of 180 degrees and 3 arc seconds for the position angle and separation of the AB pair (source for the image below):

Click on the image to enlarge it.

Click on the image to enlarge it.

Without means of obtaining a precise measure at the time, he referred the AB pair to Baron Dembowski, who measured them at 177.0 degrees and 2.81” in 1875. Burnham later measured them at 181.9 degrees and 2.62” in 1891, and R.G. Aitken came up with 178.0 degrees and 2.48” in 1898.

That gets us back to the hauntingly faint CD pair, which Burnham referred to almost parenthetically as “a very faint pair in the n p quadrant [n p is north preceding], about 100” from the primary.”  The WDS shows 1872 as the date of first measurement for AC, with a position angle of 315 degrees and a separation of 100”. Burnham didn’t measure that pair in 1872, as far as I can determine, other than to estimate their distance from the primary.  Nor does he provide any data on the CD pair in his 1900 General Catalogue of 1290 Double Stars Discovered from 1871 to 1899 (p. 94), which is the volume that lists all of the discoveries associated with his Bu (or β) prefix, and apart from alluding to their being visible in the north preceding quadrant, he also ignores the pair in the second volume of his 1906 General Catalogue of Double Stars Within 121° of the North Pole (p. 508).

But “C” is worth some attention in its own right since it appears to be passing by to the northeast at a rather determined pace.   The WDS shows it has a proper motion of +105 +069 (.105”/year east and .069”/year north), while Simbad is slightly different at +095 +069.   I came up empty handed in a search for the distance of Bu 23 — and even if it was known, there’s no assurance it would apply to “C” — so there’s really no way of putting that motion into perspective. At any rate, here’s Simbad’s plot of “C’s” proper motion relative to the AB pair:

Click on the chart to enlarge it.

Click on the chart to enlarge it.

So there you go – three stars picked pretty much at random (thanks again to Chris Thuemen for calling may attention to Gomeisa over a year ago), and all of them showing varying degrees of restlessness.  I never cease to be amazed at what I find when I start researching multiple stars. The starry heavens are filled with enough beauty and surprise to keep a person busy for several life times.

Next time – off to comb the knots out of Bernice’s hair in Coma Bernices.

Clear skies until then! :cool:

Four for Canis Major: S 537 and S 538, S 534, Nu1 (ν1)

I’m never sure where I’m headed next when I finish up in one area of the sky. Sometimes something in a star atlas will catch my eye and I’m off like a photon shot from a laser in hot pursuit, and other times I come across a book or internet reference to an intriguing multiple star that piques my curiosity.   There are other times, though, when an email lands squarely in the middle of my computer screen and grabs my full attention.

That’s what happened this time, and it led me on a chase down the same star-strewn path traveled by Sir James South almost two hundred years ago in Canis Major.   Whereas he was accompanied by a five inch f/16.8 refractor with a Tulley objective, I had the companionship of both a five inch f/9.3 Meade refractor and a six inch f/10 refractor equipped with a Jaeger’s objective – which is not to ignore the constant presence of Herr Klaus, the astro dog. I suspect the transparency of our skies was about the same, though – mine subdued with coastal moisture and his with the smoky murk of early nineteenth century Paris (the observatory he used for these observations was located at Passy).

And while I was roaming those star fields of two hundred years ago, my eye was caught by a distinctive trio of stars southwest of Sirius.   Those turned out to be the three members of the Nu (ν) family — ν1, ν2, and ν3 — one of which is a dazzling double star.

First, a look at the wide view of where we’re going:

 You’ll find Nu-1 (ν1), the last star on our tour, three degrees southwest of Sirius, wedged between its stellar siblings, Nu-2 (ν2) to its south, and Nu-3 (ν3) to its north.   But since I’m writing this in late April as Sirius sinks into the southwest, we’re going to start further south with S 537 and S 538, located west of Omicron-1 (o1) CMa, which is almost eight full degrees south and slightly east of Sirius. Hopefully by the time we work our way back up north, Nu-1 (ν1) will still be high enough for you to catch.   (Stellarium screen image with labels added, click on the chart to enlarge it).

You’ll find Nu-1 (ν1), the last star on our tour, three degrees southwest of Sirius, wedged between its stellar siblings, Nu-2 (ν2) to its south, and Nu-3 (ν3) to its north. But since I’m writing this in late April as Sirius sinks into the southwest, we’re going to start further south with S 537 and S 538, located west of Omicron-1 (o1) CMa, which is almost eight full degrees south and slightly east of Sirius. Hopefully by the time we work our way back up north, Nu-1 (ν1) will still be high enough for you to catch. (Stellarium screen image with labels added, click on the chart to enlarge it).

Here’s a close-up view of our starry hunting grounds with Omicron-1 (o1) parked down in the bottom left hand corner of the view. A short hop of three degrees due west from Omicron-1 will put both S 537 and S 538 in your field of view. If you have time, don’t neglect the ethereal starlight of M41. (Stellarium screen image with labels added, click on the chart for a larger view).

Here’s a close-up view of our star-studded hunting grounds with Omicron-1 (o1) parked down in the bottom left hand corner of the view. A short hop of three degrees due west from Omicron-1 will put both S 537 and S 538 in your field of view. If you have time, don’t neglect the ethereal starlight of M41. (Stellarium screen image with labels added, click on the chart for a larger view).

S 537/Bu 324           HIP: 32744   SAO: 172389
RA: 06h 49.7m   Dec:  -25° 05’
Identifier        Magnitudes       Separation     Position Angle      WDS
Bu 324    AB: 6.56,   7.93               1.80”                  211°               2008
S 537      AC: 6.56,   8.28             30.40”                 282°               2008
S 537      AD: 6.56, 13.00            30.60”                      3°               1999
Distance: 584.5 Light Years
Spectral  Classifications:  “A” is A0, “C” and “D” are A2

S 538                HIP: 32729   SAO: 172383
RA: 06h 49.6m    Dec:  -24° 09’
Magnitudes:  7.16, 7.18
Separation:   26.8”
Position Angle:  4°  (WDS 2007)
Distance: 622.4 Light Years
Spectral Classifications:  A6 and A2

Back to the email I referred to earlier, which is a description of S 537 and S 538:

A beautiful formation of two doubles and a single star. The top double is S 537 which is perpendicular to the line of stars, a bright and faint white double which is wide, then underneath (231″ away) is S 538, a faint and fainter white double slightly less wide, which is in line with the main line of stars, and finally adding to the overall beauty of the asterism is a faint star (mag. 8.4) which is CD-24 4476, about as away again (actually 253″). The main star of S 537 (BU 324) was resolved intermittently (‘popped out’) at 136x. The popping out was most odd. With rather poor seeing at the moment (the jet stream is very fast which makes the air turbulent) the main star was unresolved at first, then just as I was giving up, it suddenly ‘popped’ into being a pair, and then fell back to a single star again. I was rather doubtful but kept on looking and it happened again (but not thereafter).”

That picturesque description, written by Peter Morris from his London observing site, landed in my inbox on the Saturday afternoon of January 25th (2014).   And at 9PM that night, I had S 537 and S 538 cornered in a 10mm Radian:

And there they were, exactly as Peter described them – S 537 at the top of the view, perpendicularly contrasting with the vertical symmetry of S 538, and at equal distance south of S 538 is the star Peter referred to as CD-24 4476, which also goes by SAO 172832, among other designations. The primaries, by the way, were all white. (East & west reversed to match the refractor view. Click on the sketch for a much better version).

And there they were, exactly as Peter described them – S 537 at the top of the view, perpendicularly contrasting with the vertical symmetry of S 538, and at equal distance south of S 538 is the star Peter referred to as CD-24 4476, which also goes by SAO 172832, among other designations. The primaries, by the way, were all white. (East & west reversed to match the refractor view. Click on the sketch for a much better version).

Click to enlarge the image.

S 537, click to enlarge the image.

My experience with trying to separate Bu 324 was uncannily similar to Peter’s. I had an elongated glimpse of it with the 10mm Radian (152x), which led me to see what I could coax from an Astro Tech 6mm Plössl (253x). The seeing was so poor that it wouldn’t come to focus, so I reluctantly went back to the 152x view and sat as still as rock, waiting for the elongation to transform itself into two distinct stars.

I eventually got the “popping out” effect Peter mentioned, but only briefly, and only twice.   Rats – foiled again by uncooperative skies. Bu 324, by the way, was discovered in 1875 by S.W. Burnham with his six inch f/15 Clark refractor. It was first measured at a separation of 1.88” in 1877, so it has changed little, if any, since.

Click to enlarge.

S 538, click to enlarge.

The “S” designations are the result of several observations made by James South in February and March of 1825, which I’ve included at the right.  A close look at those numbers shows little change in the almost two hundred years since Sir James made his initial observations.

Translating his early nineteenth century position angles into present usage and leaving the separations as is, he measured what is now the AC pair of S 573 at 281° 51’ and 30.305” (the 2008 WDS numbers are 282° and 30.40”). For S 538, his final results were 3° 16’ and 27.806” (versus the 2007 WDS data of 4° and 26.8”).  The source for South’s observations shown at the right can be found here.

Click to enlarge.

Click to enlarge.

It took some determined detective work, but I also tracked down the first measurement of what is now the AD component of S 537 on pages 46 and 47 of this source.   Eric Doolittle made that one in 1898 from the Flower Astronomical Observatory, which was associated with the University of Pennsylvania near Philadelphia.  The “Sh” designation Doolittle used in the page shown at the left is an error — it should be shown as S 537.  “Sh” was only used to refer to the joint John Herschel-James South catalog (scroll down to the last title) published in 1824, which we’ll get to when discussing Nu11) CMa.  (The WDS has replaced “Sh” with “SHJ”).

The instrument used by Doolittle was an eighteen inch refractor with a Brashear objective, which he described as having “proved in every respect more than satisfactory.”   Again, there is little difference between his figures for the AD pair (2.45° and 30.27”) compared with the 1999 WDS figures (3° and 30.60”).

Now we’ll follow Sir South north by moving one degree northwest from S 537/538 to 6.0 magnitude HIP 32368 and then another degree northwest (slightly more north) to S 534 (here’s that earlier chart again).

S 534               HIP: 32144  SAO: 172204
RA: 06h 42.8m    Dec:  -22° 27’
Magnitudes:  6.27, 8.30
Separation:   18.2”
Position Angle:  144°  (WDS 2003)
Distance: 160 Light Years
Spectral Classifications:  “A” is F2
Note:  “A” is a variable star, V 350 CMa

You’ll find the field of view surrounding S 534 is quite a contrast to the dazzling white lights of S 537 and S 538:

 In a five inch refractor S 534 is surrounded by a rather sparse field, although it compensates with that curving arc of eighth and ninth magnitude star arrayed along its west edge. In fact, while sketching this idyllic scene I grew rather attached to that arrangement of starlight. Once again, the only color visible here was the white light of the primary. (East & west reversed to match the refractor view, click on the sketch for a larger version).

In a five inch refractor S 534 is surrounded by a rather sparse field, although it compensates with an inner and outer arc of curving stars arrayed along its west edge. In fact, while sketching this idyllic scene I grew rather attached to that delicate arrangement of starlight. Once again, the only color visible here was the white light of the primary. (East & west reversed to match the refractor view, click on the sketch for a larger version).

The outer arc of stars guarding the west side of S 534 all have names, magnitudes, and even spectral classifications. From north to south they are SAO 172191 with a magnitude of 8.86 and a spectral classification of B9; SAO 172183, 8.12, B3; SAO 172181, 9.05, AO; and SAO 172187, 9.48, K5. That second star, SAO 172183, is also a double, designated as B 1963 (magnitudes of 8.10 and 10.98, 130°, 1.2”, WDS 1991), that would be an interesting challenge for a night of steady seeing.

Click to enlarge.

S 534, click to enlarge.

James South paid three visits to the pair of stars he cataloged as S 534 around the same time he looked at S 537 and S 538. Those dates can be seen in his observation shown at the right. And again, when we compare the averaged measures made during his three observations (143° 13’ and 18.252”) with the most recent WDS measure of 2003 (144° and 18.2”), we see virtually no change in the relative positions of the primary and secondary.

The S 534 primary is also a variable, but depending on where you look you’ll find two different designations assigned to it.   Stelladoppie, which pulls its data from the WDS, lists it as V3181 (the AAVSO designation is NSV 3181), but I found the AAVSO site now lists that as obsolete.   Simbad uses the current designation, which is V 350 CMa.  The AAVSO web site shows a rather narrow magnitude range, 6.18 to 6.27, with a short period of .91041 days.

Meanwhile, on to our last star, which also has a connection to James South. Nu11) CMa lies four degrees north and slightly east of S 534, but it’s actually easier to get there by starting at Sirius, which is impossible to miss with its -1.50 magnitudes of blazing white light.  Going back to our first chart (here), you’ll find the trio of Nu (ν) stars lying from two to three degrees southwest of Sirius.  Nu1 1) is located halfway between Nu33) and Nu2 2).

Nu11) Canis Majoris  (6 CMa)  (H IV 81)  (SHJ 73)          HIP: 31564  SAO: 151694
RA: 06h 36.4m    Dec:  -18° 40’
Magnitudes:  5.79, 7.38
Separation:   17.8”
Position Angle:  264°  (WDS 2011)
Distance: 277 Light Years
Spectral Classifications:  “A” is G9

Another surprisingly sparse field, at least in a five inch refractor, but this time with what almost looks like a pair of headlights coming straight at you.   There’s a very slight, but very noticeable, yellow-gold light streaming out of the primary.   SAO 151712, over in the northeast corner, is a 7.83 magnitude K4 star. (East & west reversed, click on the sketch to improve the view).

Another surprisingly sparse field, at least in a five inch refractor, but this time with what almost looks like a pair of headlights coming straight at you. There’s a very slight, but very noticeable, yellow-gold light streaming out of the primary. SAO 151712, over in the northeast corner, is a 7.83 magnitude K4 star. (East & west reversed, click on the sketch to improve the view).

Sir William Herschel had a look at this star on September 30th, 1782, describing it with a mysterious Latin phrase “In dextro genu.”   I plugged that into the Google translator, which spit out “on the right knee” – and sure enough, that’s where Nu11) CMa is (take a look at the first chart again).   Sir William measured the separation of the two stars at 18.32” but was more elusive with his position angle, describing it as “very near directly preceding”, which actually describes it reasonably well.

Wm. Herschel on Nu-1 CMa

Click to enlarge.

Click to enlarge.

I mentioned a connection between Nu11) and James South, which is a result of a March 22nd, 1821, observation he made jointly with Sir John Herschel.   He felt there was an obvious change in position angle, a result of his measuring it at 17.24”, but with the 2011 WDS data falling almost exactly halfway between his measure and that of William Herschel forty years earlier, it’s hard to say who was closest to being correct.

As to whether those differences indicate orbital motion, or are just variations between observers, it’s possible to gain some insight by looking at the proper motions of the primary and secondary.   There’s a slight difference between the data listed in the WDS (-013 +018 for the primary, -009 +022 for the secondary) and Simbad (-010 +013 and -002 +006), but they both indicate the two stars are pretty much moving through interstellar space in parallel with each other, meaning there’s no indication of an orbital relation.   Here’s what that motion looks like on Simbad’s chart:

For those not familiar with proper motion numbers, the -013 +018 mentioned above for the primary means .013” per year west and .018” per year north, while -009 +022 for the secondary translates as .009” west per year and .022” north per year. (Click on the chart to enlarge it).

For those not familiar with proper motion numbers, the -013 +018 mentioned above for the primary means .013” per year west and .018” per year north, while -009 +022 for the secondary translates as .009” west per year and .022” north per year. (Click on the chart to enlarge it).

As for the position angle measurements by Wm. Herschel and the Herschel/South duo (their 10.8° south preceding translates to 259.2°), Sir James took issue with the senior Herschel’s description of the position angle, maintaining his “very near directly preceding” was “irreconcilable with a deviation of 10° from the parallel.”

And considering it was only an estimate, I actually thought Sir William had described it rather well.  Which just goes to show perception, as well as beauty, lies in the eye of the person at the eyepiece.

Off to the east again for the next tour as I race to catch sight of one more winter constellation before losing it to the western horizon.

Clear Skies! :cool:

A West Orion Odyssey: WEB 3, ARN 63, HJ 698, Σ 700, and HJ 697

Mysteries abound in the universe, many of them obscure and many of them subtle, and many more mind boggling beyond belief —– and then there are others that leave you shaking your head and wondering how something so obvious could have been missed so completely. To be less obscure and more direct, how do two eye-catching, very distinctive triple stars sitting five and nine arc minutes from an F.G.W Struve discovery, and twice that distance from a much fainter John Herschel discovery, end up being ignored by both of those observers? And to compound the perplexity, once both of these distinctive triple stars achieves recognition, each is cataloged as a double star. What goes on in this deep dark sector of the sky? Only the sky gods know —– and they’re not talking.

At any rate, mystifying as that situation is, it’s also very mesmerizing.  Would you believe four double and/or triples stars all within a single field of view? In fact, the farthest distance between them amounts to a mere seventeen minutes of arc.

And as long as we’re straining credulity to the breaking point, we may as well wander another one and half degrees south of that quadruple collection of multiple stars to another double star with a more – pardon the phrase – companionable mystery.

First, let’s look at the wide view in order to get ourselves oriented:

Our Orion Odyssey begins just a few degrees west of Mintaka, also known as Delta (δ) Orionis, in the area within the turquoise circle.   (Stellarium screen image with labels added, click on the chart to enlarge it).

Our Orion Odyssey begins just a few degrees west of Mintaka, also known as Delta (δ) Orionis, in the area captured within the turquoise circle. (Stellarium screen image with labels added, click on the chart to enlarge it).

And then let’s close in on our targets:

Starting at Mintaka, we’ll move northwest a distance of 40 arc minutes to 6.87 magnitude HIP 25727, then continue northwest for a full degree to 6.16 magnitude HIP 25378, and then make one more northwest leap for a distance of 52 arc minutes to reach 7.6 magnitude Σ 700. (Stellarium screen image with labels added, click to a larger view).

Starting at Mintaka, we’ll move northwest a distance of 40 arc minutes to 6.87 magnitude HIP 25727, then continue northwest for a full degree to 6.16 magnitude HIP 25378, and then make one more northwest leap for a distance of 52 arc minutes to reach 7.6 magnitude Σ 700. (Stellarium screen image with labels added, click to a larger view).

Center Σ 700 in your eyepiece at a moderate magnification, say 50x to 75x, and you’ll find a dazzling field of subdued starlight that includes these four stars:

WEB 3      No HIP number     SAO: 112705        ARN 63      HIP: 25179   SAO: 112707
RA: 05h 23.1m   Dec: +01° 17’                             RA: 05h 23.2m   Dec: +01° 08’
Magnitudes: 7.29, 10.45                                        Magnitudes: 7.97, 10.1
Separation:  62.2”                                                   Separation:  39.5”
Position Angle: 10°  (WDS 2003)                         Position Angle: 65°  (WDS 2003)
Distance: ?????                                                      Distance: 830 Light Years
Spectral Classifications: K2 and F                      Spectral Classifications: B6 and A2

Σ 700  (H I 75)    HIP: 25174   SAO: 112704        HJ 698       No HIP No.    SAO: 112688
RA: 05h 23.1m   Dec: +01° 03                               RA: 05h 22.4m   Dec: +01° 04’
Magnitudes: 7.69, 7.89                                           Magnitudes: 10.24, 13.0
Separation:  4.9”                                                      Separation:  14.2”
Position Angle: 6°  (WDS 2011)                            Position Angle: 243°  (WDS 2000)
Distance: 750 Light Years                                      Distance: ?????
Spectral Classifications: B9, B9.5                        Spectral Classification: F0
Note:  STF 700 is also known as V1804,            Note: Simbad has B at a mag. of 12.4
an Algol type eclipsing variable with a
period of 2.222878 days.

And since you can’t tell the players without a scorecard, here’s a labeled sketch of the area (there’s an unlabeled version at the end of this post, also):

Σ 700 is the dominant multiple star in this field because of its brightness relative to the other multiple stars, but ARN 63 and WEB 3 are pretty distinctive, too, even at 67x.   If any of the four multiple stars was likely to have been missed, it would be the much dimmer and difficult to separate HJ 698. White, by the way, was the only color visible, except for the very slight reddish-orange tint of WEB 3’s 7.29 magnitude primary.   (East & west reversed to match the refractor view, click on the sketch for a much better view).

Σ 700 is the dominant multiple star in this field because of its brightness relative to the other multiple stars, but ARN 63 and WEB 3 are pretty distinctive, too, even at 67x. If any of the four multiple stars was likely to have been missed, it would be the much dimmer and difficult to separate HJ 698. White, by the way, was the only color visible, except for the very slight reddish-orange tint of WEB 3’s 7.29 magnitude primary. (East & west reversed to match the refractor view, click on the sketch for a much better view).

I was wrestling with another night of poor seeing and murky skies, so the 100x I used for the inset at the right of the sketch was about as high as I could go and still maintain something resembling a focused image. Even at the 67x used for the main sketch, Σ 700 was a shaky sight, but nevertheless it was clearly elongated at that magnification. HJ 698 was also a struggle, thanks to the 2.76 magnitudes of difference between them – although I should point out Simbad lists the secondary at a magnitude of 12.4 (versus the 13.0 in the WDS), which is enough of a difference to provide some advantage given the observing conditions.

Click on the image to enlarge it.

Click on the image to enlarge it.

On the other hand, ARN 63 and WEB 3 were pure visual simplicity itself. At the low magnification I was using, I found both far more visually appealing than Σ 700 and HJ 698. If I had been looking through a telescope with either F.G.W. Struve or John Herschel in 1827, the year each of them made their measurements of the two stars with their initials attached (the senior Struve’s observation is shown at the right, J. Herschel’s is located further down the page), my eye would have been drawn north to both ARN 63 and WEB 3.  Surprisingly, though, WEB 3 didn’t receive measured attention until sometime in the last half of the 19th century (there’s another mystery here: the Reverend T.W. Webb died in 1885, but the first measure for WEB 3 listed in the WDS is dated 1909). ARN 63, on the other hand, wasn’t measured until 2003.

Apart from the fact that ARN 63 and WEB 3 were ignored by both Struve and Herschel, there are two other puzzling mysteries. One is the fact that both stars impress one as possible triple stars on first sight, and the other has to do with the 1892 date of first measurement listed in the WDS for ARN 63.

First, I should point out that it was common for many of the earlier double star observers to establish a limit for separations between components, meaning anything beyond their self-imposed limit was usually ignored. R.G. Aitken wrote an article in 1910 stating Struve’s limit was 32”, which would explain why he passed on both ARN 63 and WEB 3.   I’ve never come across any mention of what separation limit Sir John Herschel employed, but his catalogs do contain a few stars wider than both ARN 63 and WEB 3, although they’re comparatively rare (examples are HJ 980, which he measured at 70” in 1827; and HJ 1079, which he measured at 60” in 1828).

That leaves the triple aspect of ARN 63 and WEB 3 unexplained.   Again, it could be a case of the third stars exceeding the separation limits employed by the observers who first measured these two stars, although I’ve come across numerous cases of companions exceeding the distances of the third star of each of these pairs. What’s clear, however, is there never was – and still isn’t — any standardized separation limit in use from one observer to the next. Nevertheless, it would seem to make sense to extend measures to these third companions in order to provide an initial base for comparing later measurements in an effort to determine whether an orbital relation exists.

And then that leaves us with that 1892 date of first measurement in the WDS for ARN 63. When I first saw that, I assumed someone discovered and measured the star that year.   But as I looked into it further, I found the ARN of ARN 63 belongs to Dave Arnold, who was credited with being the first to measure the star in 2003. That raised the question of why a star with a first measurement date of 1892 would be assigned an identifying prefix in 2003, so I began a long search through the old star catalogs I’ve collected over the years in hopes of finding the name associated with the 1892 date – and kept running into one dead end after another.

My next step was to send an email to Dave Arnold, who graciously replied that as he measured known double stars and came across pairs he was unable to identify, he submitted them to Brian Mason at the US Naval Observatory (USNO) to determine if they had previously been measured. If not, or in a case where measures existed but no credit had ever been assigned, Brian applied the ARN prefix to the star.  Dave suggested I get in touch with Brian to see what information he had.

I had already been in touch with Brian to get the observational data for ARN 63, which also showed measurements of that pair of stars had been made in 1909, 1910, 1929, 1963, 1982, 1991, and 2000. So I contacted Brian again, asking especially about the first three dates, which I had also researched and drawn blanks on.  And at that point I learned something new and very impressive.

All of the measures for the dates prior to 2003 were determined by matching data from various astrometric catalogs kept at the U.S. Naval Observatory in Washington, D.C., which is the home of the Washington Double Star Catalog (WDS).   In other words, using their collection of catalogs, it was possible to determine position angles and separations all the way back to 1892. I’ve always had an immense amount of respect for the resources provided by the WDS, but that additional insight into the capabilities available to the USNO confirms what a priceless resource it is.

Now, on to HJ 697, which lies a short one and a half degrees south of Σ 700. Going back to our second chart again (click here to open it in a second window), with Σ 700 centered in an 8×50 finder, you should be able to catch sight of 4.74 magnitude 22 Orionis, hugged closely by HJ 697. You can also use 6.16 magnitude HIP 25378 and 5.70 magnitude HIP 25223 as visual stepping stones to navigate to it.

HJ 697           HIP: 25028   SAO: 132024
RA: 05h 21.5m   Dec: -00° 25’
Magnitudes   AB: 5.68, 13.05    AC: 5.68, 11.88
Separations  AB: 33.10”             AC: 42.30”
Position Angles   AB: 66° (WDS 2000)    AC: 118° (WDS 2000)
Distance: 1077 Light Years
Spectral Classification:  “A” is B3, “B” is G1, “C” is G3
Notes: “B” had been classified as optical.

 Both the primary of HJ 697 and 22 Orionis are white, and I found a surplus of glowing photons around both stars at 200x. “B” and “C” are easily seen, and if you look carefully, you’ll see another faint star at the southern edge of the primary.   What the heck is that??? (East & west reversed to match the refractor view, click on the sketch to improve the view).

Both the primary of HJ 697 and 22 Orionis are white, and I found a surplus of glowing photons around both stars at 200x. “B” and “C” are easily seen, and if you click on the sketch to enlarge it and look carefully, you’ll see another faint star at the southern edge of the primary. What the heck is that??? (East & west reversed to match the refractor view).

I found “B” was surprisingly easy to see for a star listed with a magnitude of 13.05.  So I checked the visual magnitude in Simbad, and found it listed there at 11.3, which may actually be brighter than what I saw. It’s hard to be sure, though, since “B” is nine arc seconds closer to the primary than “C”. At any rate, it’s magnitude is certainly brighter than 13.05.

And then there’s that “companionable” mystery star clinging to the primary at a position angle of about 165 to 170 degrees. How did it get there, how did John Herschel miss it, and how did S.W. Burnham miss it???

To start at the beginning, Chris Thuemen sent both Steve Smith and I a photo of HJ 697 a few months ago which hinted at the existence of an unlisted component at the primary’s south edge:

Click to enlarge.

Click to enlarge.

A short while later, Steve was able to get a photograph showing the mystery star very clearly:

I’ve flipped both photos to match the mirror-image refractor view shown in my sketch above.   Click on the image to enlarge it.

To avoid confusion, I’ve flipped both photos to match the mirror-image refractor view shown in my sketch above. Click on the image to enlarge it.

And of course, after seeing Steve’s photo, I wondered if it would be possible to visually detect the mystery star in a six inch refractor.  As my sketch above shows, it was, although it required some intense scrutiny and patience.  But there was no doubt it was visually accessible, which takes us back to my questions a few paragraphs back.

Sir John Herschel’s observation of HJ 697 is shown below (the source can be found here), which shows the “B” and “C” components, but makes no mention of the mystery star.   You might notice his separations for the two components are noticeably different than the current measurements, although his position angles are close (“nf 20” is equal to 70° and “sf 30” equals 120°). More than likely his numbers are estimates.

Notice that Herschel’s observation of HJ 698 is also included here.   Click on the image for a larger view.

Notice that Herschel’s observation of HJ 698 is also included here. Click on the image for a larger view.

Surprisingly, S.W. Burnham didn’t include any comments on the mystery star either, even though he observed and measured HJ 697 twice:

Click to enlarge the image.

Click to enlarge the image.

Equally mysterious is how that star could have been missed with the apertures Burnham was using.   You’ll notice two notations in the fifth column from the left, which are explained on page iv of the second volume of his 1906 General Catalogue of Double Stars Within 120° of the North Pole.   β3 refers to the 18 ½ inch Clark refractor at the Dearborn Observatory in Chicago and β5 refers to the 40 inch Clark refractor at Yerkes Observatory.   You’ll also notice he lists “B” with a magnitude of 13 in 1878, but revised it to 11.7 in 1901, which matches closely with what I observed.

As to how the mystery star got there or where it came from, the most likely explanation is it’s a background star that was hidden behind the primary when Burnham made his observations. If there was ever anyone who put an eye to an eyepiece who could have detected that star, it was S.W. Burnham.   The proper motion of the primary is almost nil (+001 +015), but perhaps the mystery star has enough proper motion to allow it come into view in the hundred plus years since Burnham made his observations.

But to stir the mystery a bit more, I came across this 1999 photograph, which also shows the mystery star quite clearly.   In fact, its position relative to all three of the HJ 697 components matches those of Steve’s photo rather closely, even though there’s an interval of fourteen years between the two photos.

 HJ 697 1999 POSS II Band N, click to enlarge.

HJ 697 1999 POSS II Band N, click to enlarge.

So I’m not sure what to think at this point, except that the sky is a strange place. You never know what you’ll find lurking around the next celestial corner.

Many thanks to Dave Arnold for his reply to my email inquiry, to Brian Mason of the USNO for supplying data and answers, to Chris Thuemen for catching sight of a speck of light in his photograph, and to Steve Smith for definitively resolving that speck of light into a star.  Chris also introduced me to the Σ 700-ARN 63-WEB 3-HJ 698 area with one of his photos, which whetted my appetite for further investigation of those stars.

Next time out, as a result of inspiration provided by another reader of these pages, we’ll wander down to Canis Major and follow in the telescopic footprints left by Sir James South.

Clear Skies and stable seeing!   :cool:

Click on the image for a larger view!

Click on the image for a larger view!

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