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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.

STT Pairs in Cepheus: OΣ 32, OΣ 436, OΣ 458, and OΣ 461

Now that we have the STT pairs in Lacerta wrapped up (here and here), we’ll finish this series by looking at four rather challenging STT objects in Cepheus. For the most part, these are going to require apertures of at least six inches in order to have a fighting chance to pry faint companions from obnoxious primarial glares, although OΣ 461 has a little something for everyone, regardless of aperture.

Let’s look at a wide view of where we’re going to spend this observing session and at the same time we’ll get our directions established since they can be confusing this close to Polaris.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

Notice Cepheus is parked to the right of Ursa Minor and Polaris in this view. Since Polaris marks celestial north, that means regardless of where you are in Cepheus, north points directly at Polaris — which also means south points in the opposite direction. If you were to look at Cepheus two or three hours after it was in the position shown here, you would notice it was rotating in a direction that takes it up and over Polaris. In the world of celestial directions, the direction the stars move is celestial west, which explains why that “W” is at the top of the directional indicator situated between Cepheus and Polaris. So what that means is the directional indicator has to keep pace with the rotation of the stars . . . and that means it essentially rotates in a counter-clockwise direction to match the rotation of Cepheus.

Also, just to remind us what’s really taking place here, the stars actually aren’t moving at all. We are, and that’s because we have our feet planted firmly on Earth, the rotation of which is the real cause of this long explanation. If you want to delve deeper into celestial directions, see Greg’s post here which goes into the subject in greater detail.

Now let’s put our directional knowledge to good use and go find our first object, OΣ 32 (STT 32), which is north (celestially speaking) of Cepheus. In fact, as the chart below shows, it’s much closer to Polaris than it is to Cepheus, so we’re going to start star hopping from second magnitude Polaris.

Stellarium screen image again with labels added, click to enlarge.

Stellarium screen image again with labels added, click to enlarge.

Our first stepping stone will be 4.26 magnitude 2 Umi (also known as HIP 5372), which is three degrees southeast of Polaris. From there, it’s just a short hop to the east of 1° 18’ to OΣ 32.

OΣ 32  (STT 32)       HIP: 8520     SAO: 282
RA: 01h 49.9m   Dec: +85° 13’
Magnitudes:  8.18, 12.5
Separation:    5.3”
Position Angle: 156° (WDS 2000)
Distance: 709 LY (GAIA)
Spectral Class:  A is A5

You’ll have to look at the 408x inset at the right to see the elusive secondary of OΣ 32. North and south are reversed in this SCT view, click for a larger version of the sketch.

You’ll have to look at the 408x inset at the right to see the elusive secondary of OΣ 32, which is parked at about the seven o’clock position.  North and south are reversed in this SCT view, click to enlarge and make it easier to see the secondary.

My first look at the field that contains OΣ 32 was with an 18m Radian (136x) in a 9.25 inch SCT, which doesn’t exactly provide the widest field of view in the universe.  Because the secondary couldn’t be seen at that magnification, it was a bit difficult to establish which star was OΣ 32, and it didn’t help that I was looking at a confusing field of stars of similar magnitudes. I finally pinned it down with the help of the three 8.5 to 9th magnitude stars running along a northeast-southwest line across the lower part of the field of view in the sketch and then moving due north from the middle of the three to OΣ 32.

Then began the difficult work of prying the secondary loose from the primary. My first glimpse was a brief averted vision glimpse with a 10mm Radian (240x). The secondary became more distinct at 408x, although it was on the fuzzy side. Because of the interfering 408x primarial glare, it was impossible to compare the magnitude of the secondary with other stars, but given the difficulty it’s possible the secondary is as much as five magnitudes fainter than the primary. The only photometric data I could find on the secondary was a NOMAD1 Vmag of 15.030, which certainly is too faint because that magnitude is well beyond the reach of the 9.25 inch SCT I was using.

It’s interesting to look at the relative motion of the primary and secondary. As the data on the right side of the chart below shows the separation is clearly becoming tighter while at the same time the position angle is edging toward the south, which would indicate the secondary is slowly moving north and west (more west than north) relative to the primary.

Click to enlarge.

Click to enlarge.

And a look at the proper motion data for both stars not only shows that to be the case, but it also shows the primary is moving northeast at the same time – basically in the opposite direction – which has the effect of amplifying the gradual change in position angle and separation. Using the latest GAIA coordinates, dated 2015.0, and comparing them with 2MASS coordinates dated 1999.899, the resulting proper motion data is +013 +014 for the primary (.013” east/yr, .014” north/yr) and -.013” +009” for the secondary (.013” west/yr, .009” north/yr), which confirms the motion necessary to produce the changes in separation and position angle we see.

It’s almost tempting to think of the secondary as being in a very long period orbit around the primary, but the opposing motion of the two stars argues against that.  A parallax for the secondary would provide some valuable insight here, but unfortunately that data isn’t available yet from GAIA. So with the information we have now, it appears OΣ 32 is an optical pair.  It also appears the two stars are at or near their closest separation now and before long, that separation will begin to increase.

We’ll move back to Cepheus now and start the search for our next star, OΣ 436 (STT 436), from 3.2 magnitude Beta (β) Cephei (here’s our last chart once more). With that star centered in our finder, the first reasonably bright star we see to the northwest is 7.1 magnitude HIP 105490, located 1.5 degrees away. Continuing in the same direction for a distance of 3° 17’, with a very slight northerly tilt, we reach 6.9 magnitude HIP 104458. From there we’ll bend our direction of travel directly to the north a distance of one degree to reach seventh magnitude OΣ 436, which sits halfway between HIP 104458 and 5.9 magnitude HIP 104968.

OΣ 436  (STT 436)      HIP: 104667   SAO: 9990
RA: 21h 12.1m   Dec: +76° 19’
Magnitudes: 7.09, 11.0
Separation: 11.9”
Position Angle: 227°  (WDS 2003)
Distance: 574 LY (Simbad)
Spectral Class:  A is B9

You’ll probably have to enlarge this sketch in order to see the faint secondary parked at the eleven o’clock position right next to the primary. There’s a 13th magnitude star a bit farther away at the edge of the primary’s glare, also at the eleven o’clock position, which is not cataloged as part of OΣ 436 . North and south reversed once more to match the SCT view.

You’ll probably have to enlarge this sketch in order to see the faint secondary parked at the eleven o’clock position right next to the primary. There’s a 13th magnitude star a bit farther away at the edge of the primary’s glare, also at the eleven o’clock position, which is not cataloged as part of OΣ 436 . North and south reversed once more to match the SCT view.

Considering the WDS magnitude difference and separation for this pair, I found prying the secondary out of the primarial glare to be a bit more difficult than I expected. Looking around for something to compare with the secondary, my eyes were drawn to UCAC4 832-019368, which appeared to be similar in brightness, and possibly slightly fainter, than the secondary. The UCAC4 catalog lists that star with a Vmag of 11.505, so it’s quite possible the WDS magnitude of 11.0 for the secondary may be a half magnitude too bright, which would account for the unexpected difficulty I had in seeing it. But given the glare from the primary, the difficulty of visually estimating within a half magnitude makes it rather hard to come to a firm conclusion.

Otto Struve discovered this pair in 1848, taking three measures of it, which averaged out to a separation of 11.61” and a position angle of 230.3°. Baron Dembowski measured it in 1868 at 11.66” and 230.0°, followed by W. J. Hussey in 1898 with 11.91” and 229.2° (those numbers come from p. 177 of Hussey’s book on Otto Struve’s double stars). So when compared with the 2003 data of 11.9” and 227°, which is the most recent listed in the WDS catalog, this pair is remarkably stable.

Now we’ll head into the southeastern corner of Cepheus, which is more densely populated with stars thanks to it’s location at the edge of the Milky Way.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

We’ll start with 3.5 magnitude Zeta (ζ) Cephei, hop northward 1 degree to 5.05 magnitude Lambda (λ) Cephei, and then make a right angle turn to the west and hop another full degree to reach OΣ 461 (STT 461).

OΣ 461  (STT 461)  (15 Cep)     HIP: 108925   SAO: 34016
RA: 22h 03.9m   Dec: +59° 49’
Identifier          Magnitudes        Separation             PA         WDS Data

AB: 6.66 11.40 11.00” 297° 2011
AC: 6.66 10.03 89.90” 40° 2011
AD: 6.66 7.84 184.30” 72° 2011
AE: 6.66 6.96 237.40” 37° 2011
AG: 6.66 14.30 17.50” 335° 2007
EF 6.96 8.14 192.60” 33° 2011

Distance: 1469 LY (Simbad)
Spectral Classes: A is B1, D is A, E is A0

I’ve written about OΣ 461 before (here), so I’ll mainly concentrate on the B and G components here, which were the main focus for this project.

The B component is rather obvious at the one o’clock position in this sketch, but you’ll have to look closer to pick out the much fainter G component, both of which are labeled in the box on the right side of the sketch. There’s plenty of competition for your eye in this view with lots of scattered light radiating from the D and E companions. North and south reversed again to match the SCT view, click to enlarge.

The B component is rather obvious at the one o’clock position in this sketch, but you’ll have to look closer to pick out the much fainter G component, both of which are labeled in the box on the right side of the sketch. There’s plenty of competition for your eye in this view with lots of scattered light radiating from the D and E companions. North and south reversed again to match the SCT view, click to enlarge.

I had no problem picking B out of the 6.66 magnitude glare of the primary – it was easy with averted vision at 204x and 240x, and it popped into direct vision view at 408x. I noticed UCAC4 749-071975, shown below and to the left of the primary in the sketch, was similar in brightness to B. The UCAC4 catalog lists a Vmag of 12.114 for the comparison star, an f.mag of 11.784, and its J and K magnitudes compute to a visual magnitude of 11.906.  All of those values tend to suggest the B component is slightly fainter than the 11.40 value assigned to it in the WDS.

Based on the 14.3 magnitude assigned to it in the WDS, I really didn’t expect to see the G component, so I wasn’t surprised to find it was invisible when I first looked for it at 240x. After I increased the magnification to 408x, my prying eyes latched on to it with averted vision, and when I went back to 240x, I was able to catch it again with averted vision. If it was really a 14.3 magnitude star, G would have been beyond the reach of the 9.25” SCT, especially given the glare of the primary. The UCAC4 catalog lists an f.mag of 13.321 for it, and URAT1 lists a more optimistic f.mag of 12.97. Neither catalog shows a Vmag for the star, but both have the same J and K magnitude values for it, which works out to a visual magnitude of 13.237. Even that would have been tough to see in the glare of the primary, so I suspect the actual visual magnitude is in the 13.0 range.

Regardless of whether you succeed in picking out the G component with whatever scope you’re using, it’s worth ratcheting up the magnification to the 400x range just to enjoy the magnified spectacle of white light pouring out of the primary and its D and E companions.  Don’t pass up that chance — OΣ 461 is really a spectacular grouping of stars.

Our last Otto Struve discovery on this tour is OΣ 458 (STT 458), which is a short one degree hop due west from OΣ 461 (here’s our last chart again). You can use 7.85 magnitude SAO 33939 as a reference point to keep you on course.

OΣ 458  (STT 458)     HIP: 108301   SAO: 33894
RA: 21h 56.5m   Dec: +59° 48’
Magnitudes   AB: 7.20, 8.41   AC: 7.20, 12.60
Separations   AB: 1.00”          AC: 21.60”
Position Angle  AB: 348° (WDS 2014)   AC: 24° (WDS 2003)
Distance: 1469 LY (Simbad)
Spectral Class:  A is A0

stt-458-sketch

The goal here was the C companion, which wasn’t all that difficult given it’s distance and cooperative magnitude.  But splitting the tight AB pair was a real bonus and not as difficult as I expected it to be. North and south reversed once again, click to improve the view.

UCAC4 749-070690 caught my eye when I was looking for a comparison star for the C component of OΣ 458. The UCAC4 labeled star has a Vmag of 12.119, an f.mag of 12.011, and its J and K magnitudes work out to a visual magnitude of 11.620. The C component looked a bit fainter than the UCAC4 star, so it appears likely the WDS magnitude of 12.60 for it is about right.

Click to enlarge.

Click to enlarge.

What is now labeled as the AB pair of OΣ 458 was first measured in 1845 by Johann Heinrich Mädler with an erroneous position angle of 44.6 degrees, which also included a remark by Mädler that he was uncertain if the star he measured was elongated. The WDS shows the first recorded measure of the pair was in 1846 (350° and .7”). Hussey shows Otto Struve measuring the pair in 1851, but as you can see in the excerpt at the right from Hussey’s book, the 1851 measures appear to be in error in comparison to the measures made in 1870, 1878, 1889, and 1898. Also shown in the excerpt from Hussey’s book is S.W. Burnham’s initial 1878 measure of what is now the C component at 32.9° and 22.71”.

Looking at the apparent widening separation of the AB pair, it appears there’s some relative motion of the two stars taking place. URAT1 shows the primary with proper motion of +053 +017 (.053”/yr east, .017”/yr north), but neither it or GAIA shows any proper motion data for B, nor do they include coordinates for it. There’s also relative motion taking place with respect to the A and C components, and judging by the PM data listed in URAT1 for C, +005 +011 (.005”/yr east, .011”/yr north), the primary is outrunning the C companion in a northeasterly direction – not by a lot, but enough to result in a gradual widening of the separation.

Speaking of outrunning, we’re running out of space (and time), so it’s time to wrap up this three part look at STT pairs in Lacerta and Cepheus and move on to less difficult targets which are in the range of smaller scopes. Next trip we’ll wander over to a neglected area of Andromeda and round up a wide variety of double and multiple stars, so stay tuned.

Meanwhile, clear skies and cooperative seeing!😎

STT Objects in Lacerta, Part 2: OΣ 459, OΣ 465, and OΣ 472

On to the second part of a look at some STT objects in Lacerta. In case you missed the first part, you can get to it by clicking on this link.

We’ll get started with OΣ 459 (STT 459), which is located in the southern sector of the Lacertan lizard.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

We’re going to start at 4.15 magnitude 1 Lacertae, which is located at the south tip of the constellation, and then follow the constellation diagram line that leads toward the north.  That line comes to a halt at another similarly bright star with a magnitude of 4.50 which surprisingly has no commonly used identification other than h 1746 (HJ 1746), a pleasing double star I covered a few years ago in this post. But at the moment we’re going to use it as a jumping off point to reach OΣ 459. Here’s our chart:

Stellarium screen image with labels added.

Stellarium screen image with labels added, click for a larger view.

Starting at h 1746, move west 30’ to 7.25 magnitude HIP 109543 and then continue west a full degree to reach 7.67 magnitude HIP 109014, which is paired with 7.73 magnitude HIP 109031 to the north. From that last star, a 25’ hop due west will land you on OΣ 459, which is shadowed to its south by 8.43 magnitude HIP 108833. For reference, there’s another dim pair of stars another 25’ further west, 7.65 magnitude HIP 108867 and 7.11 magnitude HIP 108695.

OΣ 459 (STT 459)      HIP: 108841   SAO: 71981
RA: 22h 02.9m   Dec: +39° 34’
Magnitudes: 8.2, 10.8
Separation:  10.6”
Position Angle: 196°  (WDS 2010)
Distance: 1884 Light Years (GAIA)
Spectral Classification:  A is A0

 The white glow of OΣ 459 and its companion is at the center of this sketch, with one of our navigational stars, HIP 108833 parked at the south edge of the field of view (left in this sketch). North and south are reversed in this refractor view, click to get a better look.

The white glow of OΣ 459 and its companion is at the center of this sketch, with one of our navigational stars, HIP 108833 parked at the south edge of the field of view (left in this sketch). North and south are reversed in this refractor view, click to get a better look.

With a difference of 2.6 magnitudes and a decently wide separation of 10.7”, this is not a difficult pair to split. I spied the secondary quickly with an 18mm Radian (84x) in my six inch refractor, but increased the magnification to 152x with a 10mm Radian in order to provide a more pleasing frame for the image. My search for a star of similar brightness to the OΣ 459 secondary eventually landed on UCAC4 649-106803, which has a UCAC4 Vmag (visual magnitude) of 11.150, so it appears the WDS value of 10.8 for the secondary is about right.

This pair was discovered by Otto Struve in 1845. He took two measures at that time, coming up with separations of 10.51” and 10.80”, and position angles of 197.8 and 196.5 degrees (p. 182 of this source). Compared with the most recent WDS measure of 2010, there’s been virtually no change in this pair, which is not surprising given its distance of 1884 light years.

Our next move is to a considerably more complicated star, OΣ 465.  To get there we first need to head north to 4.44 magnitude Beta (β) Lacertae, which is located at the north tip of the Lacertan diamond (here’s the wide view again to get you headed in the right direction).

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

From Beta (β) Lacertae, which is located at the lower left center of the chart, it’s a two degree southwest leap (2° 9’ to be precise) to OΣ 465 (STT 465). You’ll find it 38’ south and slightly east of 5.38 magnitude HIP 109521, which is the first star you’ll come to on the southwest leap that’s similar in brightness to Beta (β) Lacertae. HIP 109521 is also known as h 1741 (HJ 1741), which is another double star we’ve looked previously and is in the same post referred to in the second paragraph above. As you scan the OΣ 465 chart, notice that 4.58 magnitude 4 Lacertae and 4.44 magnitude Beta (β) Lacertae from a triangle with STT 465 at the western tip, which should help to make sure you’re in the right place.

OΣ  (STT 465)     HIP: 109586   SAO: 51749
RA: 22h 12.0m   Dec: +50° 12’
Magnitudes  AB: 7.30, 10.55   AC: 7.30, 13.30
Separation   AB: 12.80”           AC: 17.80”
Position Angle   AB: 317°  (WDS 2010)   AC: 233°  (WDS 2003)
Distance: 2118 Light Years (Simbad), 4025 Light Years (GAIA)
Spectral Classification:  A is F0

You’ll need to enlarge this sketch by clicking on it in order to catch glimpses of the B and C components. This is a pretty darn close approximation of the visual difficulty I experienced while trying to pry the two faint companions loose from the primarial glare. (North and south reversed again to match the refractor view).

You’ll need to enlarge this sketch by clicking on it in order to catch glimpses of the B and C components. This is a rather close approximation of the visual difficulty I experienced while trying to pry the two faint companions loose from the primarial glare. We’re dealing with a wider range of magnitudes here than we did on the previous star, so be prepared to strain your visual receptors just a bit.   (North and south reversed again to match the refractor view).

I’ve paid three visits to this triple star and each time was able to catch B pretty quickly in my six inch refractor with averted vision, hovering at the edge of the glare from the primary, but I needed 152x to do it. With a bit more concentration I even managed to capture it visually with direct vision for short periods.

My search for comparison stars landed on the two UCAC4 stars identified in the sketch to the west of the primary (above it in the sketch). Trying to keep B in view, whether with direct vision, or especially with averted vision, while comparing it to a similarly faint star is just a bit challenging to say the least, and can be a dubious process, as you’re about to see.  I finally decided B is about midway between the two UCAC4 stars in brightness.

UCAC4 701-104020 has a UCAC4 Vmag of 11.518 and UCAC4 702-100946 a Vmag of 12.589, which would make B about 12th magnitude, or 1.5 magnitudes fainter than the WDS value, which really seems unlikely because B didn’t impress me as being a full magnitude fainter than UCAC4 701-104020.  So it looks as though the 12.589 Vmag value for UCAC4 702-100946 may be an error. Adding to my doubts that B is 1.5 magnitudes fainter that the WDS value is the 10.546 UCAC4 Vmag for B. We never got around to measuring the magnitude of B, so I’m tempted to say the WDS value for B is probably about right, especially considering the experience I’m about to describe with the C companion.

That one was a real chore, but I managed to latch onto it a couple of times. If the 13.30 WDS magnitude is correct, there’s no way I would have seen it in my six inch refractor. More than likely it’s in the 12.7 to 12.8 range, which would be about at the limit of what I can glimpse in that scope while trying to see around the edges of the seventh magnitude glow of the primary. UCAC4 702-100946, with it’s supposed Vmag of 12.589, was nowhere as difficult to see, which is another reason I have doubts about the accuracy of that magnitude.

At any rate, comparing stars as faint as these, especially when some of them are imbedded in the glare of a primary, in order to arrive at a magnitude estimate can sometimes produce more questions than answers.  It’s no wonder I found myself muttering in the damp darkness about the fickleness of faint stellar magnitudes while fighting off visions of a comfortable seat beside a warm fire with a good book and a hot cup of tea.

I don’t know how damp the darkness was when Otto Struve measured the B component in 1848, but according to Hussey’s account (p.191) he came up with separations of 15.26” and 15.38” and position angles of 324.1 and 324.6 degrees, which is notably different from the 2010 WDS numbers of 12.8” and 317 degrees.

Click to enlarge.

Click to enlarge.

There seems to be something fickle here, too, so let’s begin by looking at the two distances I’ve listed on the last line of the data above for OΣ 465.  You’ll notice there’s a huge difference between the Simbad and the GAIA distances, but even if you go with the closest distance of the two, the primary of OΣ 465 is too far away to display any significant proper motion in the 162 years between Otto Struve’s 1848 measure and the 2010 WDS measure. I looked at some archived copies of the WDS and found there’s a consistent change in the separation and position angle of the AB pair, which is shown just above at the right.  That list shows the average of Otto Struve’s two 1848 measures, as well as 1867 and 1898 measures by Dembowski and Hussey, respectively, which come from p. 191 of Hussey’s book. It’s quite possible B is a foreground star and is slowly moving in front of the primary, which would make this an optical pair and account for the steady change in separation and position angle. GAIA doesn’t have any parallax data yet on B, so without that crucial piece of information, there’s no way to be certain at this point where it lies in relation to the primary.

As for who added C, it took some digging, but persistence paid off. The WDS shows the first measure of the AC pair was made in 1908, which is a strong hint that S.W. Burnham was involved. However, I had no luck in finding it in his 1913 Proper Motion Catalog, which is the only catalog he published after 1908. So I turned to R.G. Aitken’s 1932 New General Catalogue of Double Stars Within 120° of the North Pole and tracked down OΣ 465 on page 1364 of the second volume. And sure enough, the catalog entry identified Burnham as the source of the first measure, including the actual numbers, which match the WDS data. And unlike the AB pair, those numbers are pretty close to the 2003 measures in the WDS, which again points to B as the half of the AB pair responsible for their gradual change.

On to our last STT object in this trip through Lacerta. You’ll find OΣ 472 one degree almost due east of Beta (β) Lacertae, and you’ll skirt past the very small open cluster NGC 7296 on the way. Here’s our previous chart once again.

OΣ 472 (STT 472)     HIP: 111058   SAO: 34519
RA: 22h 29.9m   Dec: +52° 25’
Magnitudes  AB: 6.63, 11.50    AC: 6.63, 12.60
Separation   AB: 12.90”            AC: 12.50”
Position Angle  AB: 300° (WDS 2013)    AC: 356°  (WDS 2013)
Distance: 404 Light Years (Simbad, no data in GAIA).
Spectral Classification:  A is G8
Note:  AB is LEO 53, AC is STT 472

Again, you’ll have to enlarge this sketch by clicking on it and then looking closely at the one o’clock position to see a small speck of light. That’s the C component, the one discovered by Otto Struve. North and south reversed once more to match the refractor image.

Again, you’ll have to enlarge this sketch by clicking on it and then looking closely at the one o’clock position to see a small speck of light. That’s the C component, the one discovered by Otto Struve. North and south reversed once more to match the refractor image.

I’ve looked at this triple star twice, about a year apart, and had no luck whatever at spying the B component. C wasn’t easy either, but with persistent averted vision and parallax-induced patience I managed to to pry it out of the primarial glare both times. I found it was very similar in magnitude to UCAC4 713-102498, which has a UCAC4 Vmag of 12.288. So it’s possible the C component is slightly brighter than the WDS value of 12.50.

On the other hand, the B component, located at virtually the same distance as C, is pretty clearly considerably fainter than the WDS value of 11.50. The only photometric data available on B is a UCAC4 f.mag of 13.924, which is a definite hint that B is somewhere in the 13.5 magnitude range.

Click to enlarge.

Click to enlarge.

The AC pair first appeared in Otto Struve’s 1845 catalog with an estimated separation of 15” and no position angle (see excerpt at right).  The first published measure of the pair was made by Baron Dembowski in 1867, 15.80” and 365.8 degrees (p.192 of Hussey). OΣ 472 was later rejected in the second edition of the Pulkovo catalog because it was decided the separation of the pair exceeded the catalog limit of 16”, so apparently there was a measure made between 1843 and 1867.

As for the ear-catching LEO 53 (no association with Leo the Lion of constellation fame), it was pried out of the primary’s radiant glare in 1928 by Frederick C. Leonard, using the 60-inch reflector on Mt. Wilson. However, at Leonard’s request the actual measures were made by Aitken using the 36 inch Lick refractor. Leonard made a total of 56 double stars discoveries between 1917 and 1943. Because his published record of LEO 53 goes into more detail than is usual for a new double star measure, I thought it would be worth while to include it below in its entirety (source).  Notice that Leonard estimated the magnitude of B to be ±13.5 at the time of discovery.

leo-53-lick-ob-bull-no-450-16-1933-p-93

That wraps up Lacerta for now, but we’re not yet done with Otto Struve who will be back shortly to take us on a tour of four of his discoveries in Cepheus.

Clear skies and tolerable temperature!😎

STT Objects in Lacerta, Part 1: OΣ 475, OΣ 477, and OΣ 479

It’s rather ironic that I find myself back in Lacerta once again, which is the scene of the last post I wrote here several months ago. But this is an intriguing little constellation, dim though it is, and is well worth spending some time here. This time we’ll concentrate on six of Otto Wilhem von Struve’s more challenging discoveries. The challenge here isn’t feeble starlight (with one exception) as much as the more dreaded difference in magnitudes. Fortunately the stingiest separation is 10.7”, so we have a fighting chance to separate these pairs. You’ll need a minimum of six inches of unobstructed aperture to resolve these stars, although given very dark skies, great transparency, and stable seeing (in other words, rather rare atmospheric cooperation), you might get by with five inches.

As historical background, Otto Struve published the first catalog of his discoveries in 1843 with a lengthy title which was typical of the era, Catalogue de 514 Étoiles Doubles et Multiples Découvertes Sur L’Hémisphère Céleste Boréal par La Grand Lunette de L’Observatoire Central de Poulkova. Fortunately, the title which has come into common usage is The Pulkova (or Pulkovo) Catalog. This particular survey of double stars was actually started on August 26th, 1841, by Otto’s father, Friedrich Wilhelm Struve, who turned it over to his son within a month. There were several additions and modifications to this catalog over the next decades, which resulted in the printing of subsequent editions, including a supplement of much wider pairs. Also lending a hand and providing many of the measures of these pairs was Johann Heinrich Mädler.

Let’s start by getting situated in Lacerta, which lies in the dim region between Cepheus and Cygnus. Even though the area is sparse in regard to eye-catching magnitudes, the north end of Lacerta lies in a star strewn stream of the Milky Way as it meanders through Cygnus, Cepheus, and Cassiopeia.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

Note the directions indicated in the top left hand corner of this chart. Astronomical west is always the direction in which the constellations are rotating, which explains why it’s pointing in the direction shown. This is a depiction of the scene in late August or early September, when the constellations are slowly rotating toward the top of the chart.

You can also draw a line from Delta (δ) Cygni (just out of sight at the upper right of the chart) through Deneb, which will just miss the southern edge of 8 Lacerate. (Stellarium screen image with labels added, click to enlarge).

Stellarium screen image with labels added, click to enlarge.

If you’re having trouble pinning down the Lacertan Lizard, notice that a line drawn from Beta Cephei through Delta Cephei will take you right through the center of the distinctive Lacertan parallelogram. Also, a line drawn from Delta Cygni (out of view at the upper right hand corner) through Deneb will take you to the southern tip of Lacerata.

Our first stop is OΣ 477, which lies a couple of degrees north of 11 Lacertae:

Stellarium screen image with labels added, click for a better view.

Stellarium screen image with labels added, click for a better view.

If you look closely at the chart above, 4.46 magnitude 11 Lacertae forms a triangle with 6.38 magnitude HIP 111753 and 6.55 magnitude HIP 111428. OΣ 477 stands out distinctively just half a degree west of HIP 111428.

OΣ 477 (STT 477)     No HIP Number    SAO: 52303
RA: 22h 43.5m   Dec: 46° 02’
Magnitudes  AB: 7.43, 12.20   AC: 7.43, 11.24   CD: 11.24, 12.70
Separation   AB: 22.50”          AC: 182.70”         CD: 10.40”
Position Angle  AB: 262° (WDS 2015)  AC: 344° (WDS 2002)  CD: 127° (WDS 2015)
Distance: 256 Light Years (GAIA)
Spectral Classification:  A is F6

As I mentioned above, you need six inches of unobstructed aperture to spy the dim companions featured in this series. So you have to look closely to see the twelfth magnitude B companion, as well as distinguishing the difficult CD pair. Clicking on the sketch will enlarge it and make things much easier. (East and west reversed to match the refractor image).

As I mentioned above, you need six inches of unobstructed aperture to spy the dim companions featured in this series. So you have to look closely to see the twelfth magnitude B companion, as well as distinguishing the difficult CD pair. Clicking on the sketch will enlarge it and make things much easier. (North and south reversed to match the refractor image).

This was my third visit to this multiple star, and each time was an improvement over the time before. My first visit was on 8-21-2015, during which eleventh magnitude C was the only component I could catch. I came back a couple of weeks later (9-7-2015) and that time, with a determined application of averted vision, I pried 12.2 magnitude B out of the primarial glare, but still couldn’t distinguish 12.7 magnitude D clinging to C. My most recent visit, almost exactly a year after the second, was under much improved seeing conditions. Not only was B much easier to see, but D was also obvious when I looked closely. In fact all three components were such a breeze that I was surprised to see how difficult they had been when I looked at my notes from the prior visits.

Not only were the three components more cooperative, but I also picked out the faint star which is shown just to the left of B in the sketch, which was totally absent during the earlier encounters with OΣ 477. That star is identified in Aladin as UCAC4 681-126049 with a visual magnitude of 13.073. Combining the J and K magnitudes for it results in a similar magnitude of 13.021, so it’s safe to call it a 13.0 magnitude star. Again, it’s amazing the difference a cooperative atmosphere can make – sort of what you might call the difference between night and day.

By the way, a comparison of various UCAC4 and NOMAD-1 magnitudes for B, C, and D all resulted in remarkable consistency, each coming in within a few tenths of a magnitude of the WDS values, so all of the magnitudes shown in the data line above are very reliable.

Getting back to 13.0 magnitude UCAC4 681-126049, you might wonder why Otto Struve ignored that one at the time he observed B. There’s an easy answer to that question. When his father, F.G.W. Struve, started this survey of double stars, he established specific criteria, among which was a separation limit of 16” for companions fainter than ninth magnitude (p.16 of this source). Aladin shows a separation of 36.28” between UCAC4 681-126049 and the OΣ 477 primary, so that explains that. Otto Struve later added a supplement to the Pulkovo Catalog for wider pairs, but he apparently didn’t come back to this one. (The stars in that supplement were assigned a prefix of OΣΣ, which in WDS jargon has been transformed to STTA).

Of course that raises questions immediately with regard to the B and CD components since they’re well outside the 16” limit. With regard to the CD pair, the answer is pretty straight-forward: it was added in 1880, most likely by S.W. Burnham, although I haven’t been able to pin that down definitively. As for B, the answer is A – which is a cryptic way of saying that A has a lot of proper motion. In fact, that can be illustrated by the separation of the AB pair at the time of discovery in 1846, when it was a much tighter 9.6” (with a considerably different PA of 123 degrees). The most recent data, which comes from the GAIA catalog, shows the A component with a proper motion of +185 -009 (.185”/yr east and .009”/yr south), which means it’s moving eastward at a pretty good pace. The effect of that motion is easy to illustrate by using the Epoch tool slider in Aladin to compare and contrast the relative positions of the AB pair in 1846 and 2016:

Aladin image with labels added, click to enlarge.

Aladin image with labels added, click to enlarge.

Notice the red circles represent the positions of the two stars at the two dates shown. More proof that the heavens change just like everything else, albeit at a snail’s pace. Also, the separation between A and UCAC4 681-126049 in 1846 was 43”, which again illustrates why it wasn’t included in 1846 when Otto Struve measured the AB pair.

Now that we have that covered, we’ll move on to OΣ 479, also known as STT 479, AKA HN 42, AKA 13 Lacertae. Starting again at 11 Lacertae, you’ll find OΣ 479 is located 2 ½ degrees to the southeast. It and 11 Lacertae form a triangle with 4.95 magnitude 15 Lacertae. (Here’s our previous chart again).

OΣ 479 (STT 479) (HN 42) (13 Lacertae)
HIP: 112242    SAO: 52317
RA: 22h 44.1m   Dec: 41° 49’
Magnitudes: 5.21, 10.9
Separation:  14.4”
Position Angle: 130°
Distance: 256.5 Light Years (Simbad)
Spectral Classification:  A is G8 (WDS)

Again, you have to look closely to see the secondary, which is a bit more difficult than the secondary in the previous sketch. (East and west reversed to match the refractor image, click for a better view).

Again, you have to look closely to see the secondary, which is a bit more difficult than the secondary in the previous sketch. (North and south reversed to match the refractor image, click for a better view).

I had very little difficulty with this pair on the night I made the sketch above at 201x, which wasn’t the case a year earlier when I looked at it. On that night the secondary was immediately visible at 84x, but it decided to become difficult when I increased the magnification. At 152x, it vanished into the primarial glare, and then reappeared sporadically when I dropped back to 127x. It was more cooperative at 109x, but still a bit elusive, so I went back to 84x and was able to see it most of the time with direct vision, at other times only with averted vision.

There’s a huge difference in magnitude between the two stars, somewhat comparable to seeing the secondary of Polaris in a 50mm refractor. That pair has a Delta_M of 7.06 (magnitudes of 2.04 and 9.1) vs. 5.69 for this pair, which is fainter, so the comparison is not quite exact, but it will give you an idea of what to expect. However, I estimated the secondary to be at least a full magnitude fainter based on comparison with two nearby stars, which sheds some light on the comparison with Polaris. B appeared to me to be slightly fainter than UCAC4 659-108762 (which has a UCAC4 Vmag of 11.640) and slightly brighter than UCAC4 660-110091 (with a Vmag of 12.818), so the actual magnitude most likely lies somewhere in between.

William Herschel appears to have been the first to come across this pair of stars, having looked at them on October 17th, 1786. However he didn’t publish that observation until 1822, assigning a catalog number of H N 42 to it. His remarks on the pair were rather brief: “13 Lacertae has an extremely small star following, 3d class.” (p.171 of 1822 catalog). John Herschel also looked at 13 Lacertae in 1828, providing an estimated separation of 12” with a PA of 132.9 degrees. The first actual measure of the pair was made by Otto Struve in 1849. He recorded a separation of 14.57” and a position angle of 129.2 degrees. John Herschel recorded another measure of the pair that same year, turning in a separation of 14.70” and 129.1 degrees. Comparing those 1849 measures to the most recent 2012 WDS data shows very little change over the past 167 years.

On to our last star now. We’ll head south from OΣ 479 (with a bit of a tilt to the west) for a distance of 1° 40’ to 5.82 magnitude 12 Lacertae, then continue in the same direction another 1° 15’ to 4.89 magnitude 10 Lacertae, and then angle southeast for a distance of 1° 28’ to 6.03 magnitude HIP 111869. You’ll see OΣ 475 at the western corner of a triangle it forms with HIP 111869 and 6.65 magnitude HIP 111864. (The previous chart once more).

OΣ 475 (STT 475)     HIP: 111828   SAO: 72569
RA: 22h 39.1m   Dec: 37° 23’
Magnitudes  Aa, Ab: 6.83, 10.52   AB: 6.84, 10.80
Separation   Aa, Ab: 0.60”            AB: 16.10”
Position Angle  Aa, Ab: 50° (WDS 2009)    AB: 73°  (WDS 2008)
Distance: Unknown  (negative parallax)
Spectral Classification:   A is B2
Note: Aa, Ab is HDS 3216, AB is STT 475

And again you have to look closely to see the B component of this pair (it’s hiding in the glow of the primary between the four and five o’clock position). Notice both HIP 111869 and HIP 111864, which we used to locate OΣ 475, are in the field of view with it. (East & west reversed once again, click for a much better view).

And again you have to look closely to see the B component of this pair (it’s hiding in the glow of the primary between the four and five o’clock position). Notice both HIP 111869 and HIP 111864, which we used to locate OΣ 475, are in the field of view with it. (North and south reversed once again, click for a much better view).

I had little problem with the secondary during my two year-apart-observations since it popped into view immediately at 84x both times. I estimated it to be very similar in magnitude to UCAC4 638-120691 (located 9’ northwest), which has a Vmag of 11.008, so it appears the WDS magnitude of 10.8 is about right. Otto Struve first measured this pair in 1847 at 15.53” with a position angle of 72.8 degrees. John Herschel showed up here as well that same year, turning in a separation of 15.66” and a PA of 73.6”.

As for the Aa, Ab pair, good luck. A separation of .60” wouldn’t be out of reach for a large aperture dobsonian –- except for that annoying 3.69 magnitude difference between the two components. The HDS prefix refers to the Hipparcos Double Star survey, which first detected it in 1991. With a total of four observations recorded in the WDS, you can at least rest assured the secondary is really there if you launch a search for it.

Also hovering in the southwest quadrant of the field of view is an evenly illuminated pair, AG 284 (WDS 22387+3718), which has magnitudes of 9.86 and 9.94, separated by 26.3” with a PA of 230 degrees (WDS 2008 data). Your double-starred vision should have no problem latching onto those two.

That’s it for the first half of this tour – click here to continue to the second half.

Clear Skies!😎

Difficult Double Stars of the STT Variety

Back in the golden era of the late nineteenth and early twentieth centuries, when astronomy began to grow rapidly in the United States and Europe, communication with other astronomers was a slow process — especially when it took place between continents. For example, S.W. Burnham (1838-1921) sent many of his first double star discoveries of the early 1870’s to Milan, Italy, where Baron Ercole Dembowski (1812-1881) then made the first measures of those stars and mailed them back to Burnham in Chicago — a cycle which frequently took most of a year and sometimes longer. Burnham also actively published in European journals, primarily Germany’s Astronomische Nachrichten and England’s MNRAS (Monthly Notices of the Royal Astronomical Society), as did other American astronomers. Many a list of observations or manuscripts were dropped into the mail accompanied by doubt as to when, or if, it would reach its destination. Patience and confidence were virtues that came with experience, some of it no doubt learned with difficulty.

Communication between continents in this day and age is of course much faster, although publication cycles haven’t changed all that much – a paper or article sent to a publication frequently takes six months or longer to see the light of day. But the era of the internet and email creates possibilities that astronomers of Burnham and Dembowski’s day never would have dared to contemplate.

I’ve spent most of the last year putting those tools to good use, which has resulted in numerous publications in the Journal of Double Star Observers (JDSO), the vast majority of which have been in collaboration with Dr. Wilfried Knapp of Vienna, Austria. Most of those publications concern the more challenging of the double stars discovered by Otto Wilhelm Struve, which is why the articles are all titled “STT Double Stars with Large Delta_M.”

Now it’s a basic fact of life that when you push yourself beyond your comfort zone, you learn and grow in ways you never anticipated. Put more concisely, if you don’t try, you’ll never know. That applies to observational astronomy as well – in fact, especially to observational astronomy. When I first cast eyes on the list of double stars to be examined for the STT project, my initial thought was most of the faint secondaries on the list were too difficult to separate from their much brighter primaries. The astronomical term which describes that challenging difference in magnitudes between the two stars is “delta_M (or Δ_M)”, and thus the title of the papers.

Reams of material has been published about the relation between magnitude differentials (delta_M) and aperture, and numerous attempts have been made to pin down more precisely what can be detected and what can’t with specific apertures and magnitude differences. Although they’re certainly well intended, I’ve never been a big fan of those efforts, primarily because there are so many variables involved. The ability and experience of the observer, the quality of the optics, the telescope type, atmospheric conditions, altitude – all of those factors play a role that can’t be easily converted to numbers. But there’s one variable which is frequently overlooked: the accuracy of the published magnitudes.

I suspect that last one may catch many observers by surprise. But the reality is that magnitudes don’t get near the attention in double star catalogs as do separations and position angles. In fact, it’s not at all unusual in the case of the older double star discoveries, such as those of Otto Struve, for the current published magnitudes of secondaries to be in error, chiefly because they’ve been carried over from older observations, if not the original observation.

That factor was at the heart of the STT double star project. Of the approximately one hundred STT double stars we observed and measured, roughly half of the secondaries had noticeable magnitude errors, some of which were quite significant. We took two approaches to this.  One was an effort to estimate the magnitudes of the secondaries visually, using comparison stars where possible in order to arrive at our estimates.  The results of those comparisons were inconsistent, primarily because the glare from the primaries over-powered the secondaries, which for the most part were visible only with averted vision.  Attempting to hold an elusive and dim star in view with averted vision while at the same time latching onto a comparison star with the same eye is not an approach calculated to succeed every time.  The other was a photographic approach in which Wilfried utilized the facilities of a remote telescope site to determine magnitudes, as well as to produce precise measures of separation and position angle.  That approach proved to be quite accurate and dependable. 

We produced a total of eight papers for the STT series, and as each is published our results are finding their way into the WDS, resulting in a very satisfying and rewarding project.  I’ve listed the eight papers below, five of which have been published so far in the JDSO.  I’ll add links to the remaining three as they’re published. There’s a lot of detail in each of these papers, but the heart of them lies in the two tables near the end, one of which summarize the magnitude findings, and the other which summarizes the separation and position angle measures.

In addition to the STT pairs covered in the JDSO papers, there were another fourteen that didn’t find their way into publication because of other projects, so I’ve decided to cover my observations of that group in the next few Star Splitter posts. Those stars are located in Cepheus, Lacerta, and Lynx. Each of the pieces will be oriented more toward observation than the papers are, so stay tuned for a few star-hopping adventures that will provide you with a chance to test your observational talent and hopefully raise your averted vision skills a parsec or two.

JDSO Articles :

STT Doubles with Large Δ M – Part I: Gem  (with Steve Smith)
STT Doubles with Large Δ M – Part II: Leo and UMa (with Steve Smith)
STT Doubles with Large Δ M – Part III: Vir, Ser, Com, CrB, and Boo
STT Doubles with Large Δ M – Part IV: Ophiuchus and Hercules
STT Doubles with Large Δ M – Part V: Aquila, Delphinus, Cygnus, Aquarius
STT Doubles with Large Δ M – Part VI: Cyg Multiples
STT Doubles with Large Δ M – Part VII: And, Psc, Aur
STT Doubles with Large Δ M – Part VIII: Tau, Per, Ori, Cam, Mon, Cnc, Peg

Problems of a Different Magnitude in Lacerta: 8 Lacertae (STF 2922/A1459) and ROE 47

It had been a long while since I last took a stroll through Lacerta, so I had to grab my well-worn copy of Sky and Telescope’s Pocket Sky Atlas and relocate the constellation’s dim outline between Cygnus and Cepheus.   Lacerta is not one of those constellations that draws attention, which is unfortunate since the Milky Way runs through about 90% of its stellar real estate – meaning it has more than its share of double stars and open clusters. I was back to check on the Lacertan lizard once again because of a question about the magnitude of one of the components of 8 Lacertae, which in keeping with Lacerta’s rich stellar tradition, also has more than its share of stellar companions.   And as long as I was there, I decided to poke around and see what else I could see, which led to a magnitude of additional questions.

Even though it’s the first part of December as I write this, from my forty-five degree latitude Lacerta is almost directly overhead at 7 PM, parked in a holding position between Cygnus, Andromeda, and Pegasus, and Cepheus.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

A line drawn from Beta (β) Cephei through Zeta (ζ) Cephei will actually lead you directly to 8 Lacertae:

You can also draw a line from Delta (δ) Cygni (just out of sight at the upper right of the chart) through Deneb, which will just miss the southern edge of 8 Lacerate. (Stellarium screen image with labels added, click to enlarge).

You can also draw a line from Delta (δ) Cygni (just out of sight at the upper right of the chart) through Deneb, which will just miss the southern edge of 8 Lacerate. (Stellarium screen image with labels added, click to enlarge).

But because Lacerta is a dim constellation . . . . . .

Stellarium screen image, labels added, click for a larger view.

Stellarium screen image, labels added, click for a larger view.

. . . . . . you might find it easier to aim an 8×50 or 9×50 finder at 4.5 magnitude 6 Lacertae, move northeast a few degrees to 4.5 magnitude 11 Lacertae, and then drop southeast to 5.1 magnitude 13 Lacerate, using 5.0 magnitude 15 Lacertae as a reference point, and then move south to 5.3 magnitude 12 and 4.9 magnitude 10 Lacertae, which form a triangle with sixth magnitude 8 Lacertae parked in the west corner.   That way you’ll be sure to land on the right star at least.   There should be little chance of confusing 8 Lac with another star since “A”, “B”, and “E” are bright and very obvious:

8 Lacertae  (AB is H IV 86)      HIP: 111546   SAO: 72509
RA: 22h 35.9m   Dec: +39° 38

Identifier      Magnitudes      Separation    PA   WDS
STF 2922 AB:      5.66,  6.29          22.40″   185°   2014
A 1469 AC:      5.66, 10.38          48.90″   168°   2014
A 1469 AD:      5.66,   9.09          81.60″   144°   2014
A 1469 AE:      5.66,   7.25        337.80″   239°   2011
DAL 28 AG:      5.66, 14.08          78.60″   194°   2012
COM 8 BF:      6.29, 10.97         127.60″   175°   2012
A 1469 CH:    10.38, 14.60            1.40″   254°   1932
A 1469 DI:      9.08, 13.30          10.10″   227°   2012
DAL 28 GJ:    14.08, 12.99            6.10″    78°   2009

Distance:  “A” is 2160 Light Years; “E” is 428 LY (Simbad)
Spectral Classifications:  “A” and “B” are B2, “D” is A0, “E” is F0
Notes: Mag of I changed from 11.0 to 13.3 as of 10-29-2015
Magnitudes of GJ are reversed in WDS, should be 12.99 and 14.08

In a mid-October email from Mike Hyrczyk via Chris Thuemen, Mike mentioned he had looked at 8 Lacertae and found the “I” component wasn’t visible in his six inch refractor. At the time, it was listed in the WDS at a magnitude of 11.0, normally well within reach of a six inch scope. That evening, I pointed my six inch f/10 refractor at the complex star and, at 152x, confirmed Mike’s observation. I tried higher magnifications – 253x, 365x, and 380x – and may have had a brief glimpse of the fickle star, but there was no doubt it was fainter than the WDS’s 11.0 magnitude. Chris used a 9.25 inch SCT the following night and basically had the same experience, although he may have detected an elongation in the DI pair. Chris also noticed the magnitudes of the GJ pair were reversed in the WDS, which hasn’t been corrected as of this writing.

Given the 10.10” separation listed for the DI pair, experience told me that a magnitude of 13.0 was about the brightest “I” could be, if in fact I had actually seen it with my six inch refractor in the combined AB glare. A check of photometry records in the UCAC4 catalog showed magnitudes of 13.828 (f.mag) and 13.598 (J and K converted to visual), which were too faint for me to have had a glimpse of the star. I sent what information I had to Bill Hartkopf at the USNO/WDS, who consulted additional photometry records, arriving at a magnitude of 13.30 for “I”.

So — after that long introduction, it’s about time we took a look:

“A”, “B”, and “E” are the stars that catch your eye on first view, all of which are white, followed by “C” and “D”. You have to look a bit closer to get your first glimpse of “F”. The missing “I” component is both too faint and too close to “D” to be seen, as discussed above. There are two more faint pairs to the south of 8 Lac, neither of which are not cataloged in the WDS as double stars. (East & west reversed, click on the sketch for a better view).

“A”, “B”, and “E” are the stars that catch your eye on first view, all of which are white, followed by “C” and “D”. You have to look a bit closer to get your first glimpse of “F”. The missing “I” component is both too faint and too close to “D” to be seen here. There are two more faint pairs to the south of 8 Lac, neither of which are cataloged in the WDS as double stars. (East & west reversed, click on the sketch for a better view).

There’s also an excellent photo and discussion of the 8 Lacertae complex on page 52 of the November issue of Sky and Telescope. Sue French was unable to see “I” with a 10 inch reflector, but found a fifteen inch scope brought it into view, which supports the WDS magnitude change to 13.30.   Sue also noticed the error in the WDS listing for the GJ pair.

8 Lacertae has an interesting history. Sir William Herschel was the first to record it for posterity, cataloging the AB pair as H IV 86 in 1782 (source, sixth title from the top):

Wm. Herschel on 8 Lac

His 84° 30’ south preceding works out to a present day figure of 185° 30’, which is a good match with the current WDS figure, but his separation of 17” 14’” puts the AB pair five arc seconds closer than the WDS data. He describes six stars, which probably correspond to the A through F pairs, although his description of their relative magnitudes is difficult to follow. The Latin phrase at the top of his catalog entry translates as “In the middle of the tail”, which seems to indicate a slightly different configuration for Lacerta than what I show above in the first chart.

Click to enlarge the image.

Click to enlarge the image.

Sirs John Herschel and James South made two observations of 8 Lacertae in September of 1823, which are shown at the right (source, last title on page).  Their measures of AB, which are summarized near the bottom of the page, are in line with the current WDS data, as are their measures of the AD pair (145° 15’, 82.52”, which they refer to as AC).   They seem to have entirely missed the closer 10.38 magnitude star now referred to as “C”.

At the bottom of that same page, they refer to an erroneous measure of the AB pair made by Piazzi in 1800 (212° 58’ and 19.072”). Admiral W.H. Smyth also refers to that error on pp. 519-520 of his Bedford Catalog, as well as William Herschel’s 1782 PA error. Relying on his distinctive pre-Victorian vocabulary to make the point, he wrote: “Here the anomalies are palpably owing to error, and the fixity of the objects appears unquestionable.”

The Admiral was irrefutably correct in regard to the “unquestionable fixity” of the objects.   Given the 2160 light year distance of “A”, little proper motion is exactly what would be expected.   Simbad doesn’t provide a distance for “B”, but it does show “E” to be at 428 light years, which is also far enough away that minimal proper motion would be the norm. I checked the most recent PM data available, which comes from the USNO’s URAT1 catalog, and it confirms the minimal motion for each of the stars:

8 Lac PM Data

Aladin image with labels and data added, click to make the text more legible.

“E” shows the most motion, which again is to be expected since it’s four times closer to us than “A”.   There are no parallaxes available in Simbad on the other components of the system, but judging by their slight motion, they may well be about the same distance as “A”. And at those distance, it’s impossible to come to any conclusion on shared physical motion based on the PM numbers.

Before heading out into the night air to look at 8 Lacertae, I used Sky Tools 3 to take a quick look around the neighborhood for other interesting stars, and quickly found an intriguing multiple star, ROE 47, located just 41’ to the west (here’s our third chart again).   So give your scope a careful nudge in that direction and you’ll be greeted by a sixth magnitude star with several faint companions.

ROE 47        HIP: 111259   SAO: 72446
RA: 22h 32.4m   Dec: +39° 47’

Identifier    Magnitudes    Separation    PA   WDS
ROE 47 AB:    5.90, 11.46        42.90″   155°   2012
ROE 47 AC:    5.90, 12.40        33.50″   341°   2012
ROE 47 AD:    5.90, 12.20      103.70″   216°   2010
FYM 109 AF:    5.90, 14.11        22.00″   106°   2012
ROE 47 DE:  12.20, 12.30          6.60″   175°   2012

Distance: 684 Light Years
Spectral Classification:  “A” is A6
Notes: Mag of C changed from 10.2 to 12.4 as of 10-29-2015
Mag of D changed from 11.36 to 12.2 as of 10-29-2015
Mag of E changed from 9.90 to 12.3 as of 10-29-2015

This one had what you might call a magnitude of problems, but before wrestling with that issue, let’s take a look:

 “A” was very white; “C” was very faint and mainly an averted vision apparition; “B” was distinct; and “D”, which was just a bit easier to see than “C”, was marginally duplicitous at 152x, but it cooperatively separated at 253x with a 6mm Astro-Tech/Sterling Plössl, as shown in the insert below the insert at the right. (East and west reversed once more, click on the sketch to improve the view considerably).

“A” was very white; “C” was very faint and mainly an averted vision apparition; “B” was distinct; and “D”, which was just a bit easier to see than “C”, was marginally duplicitous at 152x, but it cooperatively separated at 253x with a 6mm Astro-Tech/Sterling Plössl, as shown in the insert below the insert at the right. (East and west reversed once more, click on the sketch to improve the view considerably).

It didn’t take but a few seconds to realize that some of the fainter components I was looking at were fainter than the WDS data said they were. As the “C” component flickered in and out of view, I could see it was clearly fainter than the 10.2 magnitude then listed for it in the WDS. There was also something clearly amiss with “D”, which wavered between direct vision and averted vision, meaning it was also fainter than the WDS’s 11.36. And “E”, which was listed at a magnitude of 9.9, was not the conspicuous speck of light it should have been – in fact, it should have been over-powering “D”.   After I separated the DE pair at 253x, it was clear they were both about the same magnitude – so 9.90 was nowhere close to being correct. Chris Thuemen also looked at ROE 47 and basically came to similar conclusions.

There’s a huge amount of photometric data available in both the NOMAD-1 and the UCAC4 catalogs, so I turned to both of those to see what I could find.   Looking at “C”, I found data pointing to a magnitude of 12.3. In the case of the DE pair, the UCAC4 Vmags, which are normally very dependable in this range, showed 11.358 for both stars, which seemed too bright to me.   The UCAC4 f.mag and the J & K visual approximations pointed toward a magnitude of 11.9 to 12.0, which struck me as being closer to what I had seen.

ROE 47 Data Mirror Image

Click to enlarge and make the data more legible.

I sent off what I had to Bill Hartkopf at the USNO/WDS, who used additional data to make the changes I’ve listed at the bottom of the ROE 47 data above. Incidentally, Bill is always quick to say he appreciates these observations very much. With the WDS data base approaching something like 130,000 stars, the only way these kinds of errors get corrected is when visual observers note the discrepancies and report them to the WDS.

Click to enlarge the image.

Click to enlarge the image.

Digging into the history of ROE 47, it appears the AB and AD pairs were discovered in 1895 by E.D. Roe, Jr., a British amateur astronomer, who used a six inch refractor. He added the “C” and “E” components in 1910, as shown in the excerpt at the right from a 1911 issue of the Astronomische Nachrichten.

I couldn’t find any biographical material on E.D. Roe, but it appears he must have had an astronomically dry sense of humor.   If you look at the top left hand corner of the image above, you’ll see he used the Greek symbol “ρ” as an identifier, which in Greek is pronounced rho, as in Roe.  Obviously he liked a good laugh.

Next trip – who knows. The winter rains are here and the few clear skies I’ve seen have had more dancing and twinkling stars than an out of control strobe light at an all-night dance party, meaning atrocious seeing, which is not usual for this time of the year. As soon as the weather cooperates (raining hard now with 60mph gusts of wind), I’ll see what I can find to grace the pages of this blog.

Until then, Clear and Cooperative Skies!  😎

Sleuthing in Sight of Sadalmelik: OΣ 460, Σ 2862, and Σ 2855

If it seems like we’ve been here before, it’s because we have – just a month shy of a year ago, when we looked at “The Alpha-Beta-Gamma of Aquarius,” and discussed Homer-era Greek grammarians, urns of olives, and wine. Those who believe double star discussions have to be relegated to dry recitations of arrid statistics haven’t spent a night with a few ancient Greek star gazers.

On that trip, we discovered Sadalmelik, aka Alpha (α) Aquarii, means “lucky stars of the king”.   Some of that luck seems to have spread to a few nearby stars in the rarified void surrounding Sadalmelik (we’re outside the Milky Way here, so star populations are sparse). I accidentally stumbled over the first lucky star, a tantalizing triple, while surveying some of Herr Otto Wilhelm von Struve’s more difficult discoveries, and it didn’t take long to discover his father, Friedrich Georg Wilhelm von Struve, had also found a couple of visually stunning stars. All three of the stars we’re about to look at are within a two degree radius of Sadalmelik, which will serve as our star base.

Stellarium screen image with labels added, click to enlarge.

Stellarium screen image with labels added, click to enlarge.

Aquarius is a dim and meandering constellation spread out over several acres of sky.   You’ll find it below the west edges of Pegasus and Cetus and north of Capricornus.   Focus your attention on the turquoise α (Alpha) in the chart above because we’re not going to wander far from it.

Here are the locations of our three stars, all labeled in tempting turquoise:

Stellarium screen image with labels added, click for a larger view.

Stellarium screen image with labels added, click for a larger view.

We’ll going to start in the north and work our way south, so let’s move north to OΣ 460, which is located two degrees due north of Sadalmelik. Use 7.57 magnitude HIP 109044 and 6.99 magnitude HIP 109052 to point you in the correct direction. You’ll find OΣ 460 lying in the center of a dim, but distinctive arc of three stars; 7.24 magnitude HIP 109144 lies on its east side, and 8.39 HIP 108990 brackets it on its west side.

OΣ 460 (STT 460)    HIP: 109064   SAO: 127283
RA: 22h 05.7m  +01° 47’
Magnitudes   AB: 8.40, 12.80    AC: 8.40, 12.10
Separations   AB: 13.80”           AC: 18.80”
Position Angles      AB: 340° (WDS 2003)    AC: 30°  (WDS 2003)
Distance: 867 Light Years (Simbad)
Spectral Classification:   “A” is F0

After several frustrating attempts to split some uncooperative sub-arcsecond pairs, I went in search of this tantalizing triple star as a diversion.   My first glance into the eyepiece showed a single star, but when I averted my vision slightly, both “B” and “C” suddenly materialized from out of the primarial glare, which, after wrestling with stars that refused to separate, was a very welcome sight:

Averted vision beauty! You have to look closely to catch sight of the “B” and “C” components, just as I did when peering into the eyepiece. The primary is a weak shade of white. Notice the two UCAC4 labeled stars, which we’ll come back to shortly. (East & west reversed to match the refractor view, click on the sketch for a better view of the faint components).

Averted vision beauty! You have to look closely to catch sight of the “B” and “C” components, just as I did when peering into the eyepiece. The primary is a weak shade of white. Notice the two UCAC4 labeled stars, which we’ll come back to shortly. (East & west reversed to match the refractor view, click on the sketch for a better view of the faint components).

I doubled the magnification with a 5mm eyepiece in hopes of pulling “B” and “C” out of the subdued glare of the primary, which resulted in this slightly improved view:

Although they’ve moved up to direct vision objects, you still have to look closely to catch “B” and “C”. (East & west reversed once again, click to improve the view).

Although they’ve moved up to direct vision objects, you still have to look closely to catch “B” and “C”. (East & west reversed once again, click to improve the view).

 (Click to enlarge)

(Click to enlarge)

At 304x, I was able to confirm my 152x impression that both “B” and “C” are brighter than the magnitudes shown above from the WDS.   Even though it was an averted vision object at 152x, “B” was too conspicuous in my six inch refractor for a 12.8 magnitude star, especially considering it’s parked within 14” of a primary listed as being four magnitudes brighter.   In fact, when compared with the two UCAC4 labeled stars in the first sketch (here it is again), both of which are in the 11.2 to 11.4 magnitude range, “B” was of about the same brightness, allowing for the glare of the primary. I found “C” was slightly brighter than “B”, perhaps in line with the .7 WDS magnitude difference between them, suggesting a magnitude for C in the range of 10.6.

A quick look at the excerpt above at the right from S.W. Burnham’s 1913 Proper Motion Catalog shows he estimated the magnitude of “B” at 11.7 and “C” at 11.0, which is similar to my estimates. STT 460 is part of a joint survey of Otto Struve’s pairs with high magnitude differentials (delta_M) I’m working on, so it will eventually be suggested to the WDS for magnitude revisions.

A glance at the proper motion of the three stars of OΣ 460 shows they appear to be unrelated, since all three are moving in different directions and at differing rates of speed.

A:  +036 -040   (WDS)         (.033”/year east, .038”/year south)
B:  -031 +142   (WDS)         (.031”/year west, .142”/year north)
C: +027 +001   (WDS)         (.027”/year east, .001”/year north)

Now we’ll drop down to Σ 2862, which lies a bit more than a degree (1° 16’) south and very slightly east of OΣ 460. You’ll find it just 24’ east of 6.99 magnitude HIP 109052. (Here’s our previous chart again).

Σ 2862        HIP: 109186    SAO: 127306
RA: 22 07.1m   Dec: +00° 34’
Magnitudes:  8.04, 8.41
Separation:   2.5”
Position Angle: 95°  (WDS 2011)
Distance: 256 Light Years (Simbad)
Spectral Classification: “A” is F8

Spare beauty in a sparse field is the best way to describe this delicate pair:

The primary and secondary are white, almost touching one another, separated by the width of B. It always amazes me how frequently surrounding stars arrange themselves into eye-catching geometric configurations – notice the three stars pointing into the west, lined up almost perfectly with one another. The moon was at first quarter when I made this sketch, about 40 degrees to the west, with moisture practically dripping out of the air, so some of the background stars undoubtedly were obscured at the time. (East and west reversed once more, click to improve the view considerably).

The primary and secondary are white, almost touching one another, separated by the width of B.  It always amazes me how frequently surrounding stars arrange themselves into eye-catching geometric configurations – notice the three stars pointing into the west, lined up almost perfectly with one another. The moon was at first quarter when I made this sketch, about 40 degrees to the west, with moisture practically dripping out of the air, so some of the background stars undoubtedly were obscured at the time. (East and west reversed once more, click to improve the view considerably).

This pair of stars was discovered and measured in 1828 by F.G.W. Struve.   The WDS identifies it as a physical double, which appears to be based on the similar proper motions of the two components.   The WDS data shows “A” with a rate of +078 +049 (.078”/yr east, .049”/yr north) and “B” with a rate of +088 +047 (.088”/yr east, .047”/yr north).

Shown below is a list of measures in Thomas Lewis’s book on Struve’s stars, to which I’ve added two additional measures that I pulled from S.W. Burnham’s 1906 catalog (labeled LM and Hu), three from R.G. Atiken’s 1932 catalog, and four which come from WDS data.

 Click on the image in order to see the data more clearly.

Click for another view.

Based on the proper motion of the two stars, there should be very little detectable change in the relative positions of the two components.   The separation measures in the list above are relatively stable in the 2.3” to 2.5” range, but surprisingly the position angle has consistently moved in a northward direction.   That would lead to the conclusion that either the proper motions numbers are slightly off, or that that one of the two stars could be in a very wide orbit around the other. Some of the preliminary GAIA data is available now in Vizier (the catalog code is I/324) so I checked and found that, unlike the WDS, it lists both stars with the same proper motion, +088.7 +046.6, numbers which are at least similar to the WDS.   At any rate, it’s possible these two stars are doing something more than just traveling the through the galaxy in tandem.

Our last star lies a little over a degree (1°7’) south of Sadalmelik (our chart once again). Drop a short 38’ south and slightly west to 5.29 magnitude 32 Aquarii and then another 32’ south and slightly east to reach Σ 2855, using 9.21 magnitude SAO 145857 to guide you. Notice Σ 2855 forms a triangle with two faint stars, 8.51 magnitude HIP 109141 and 8.93 magnitude SAO 145864.

Σ 2855 (STF 2855)    HIP: 109038    SAO: 145859
RA: 22h 05.3m   Dec: -01° 25’
Magnitudes   AB: 8.34, 10.26     AC: 8.34, 10.80
Separations  AB: 25.10”             AC: 85.10”
Position Angles   AB: 305° (WDS 2013)    AC: 117° (WDS 2013)
Distances   A: 494 Light Years    B: 109 Light Years
Spectral Classifications:   “A” is F8, “B” is G

Spare beauty once more, but we also find ourselves entranced again by a captivating geometric configuration:

The primary was a faint white, and easily the brightest star in a sparse field, while “B” and “C” seemed to be intent on getting lined up perfectly. The first quarter moon mentioned above also had something to do with the lack of stars seen in the field. (East & west reversed once more, click for a much better view).

The primary was a faint white, and easily the brightest star in a sparse field, while “B” and “C” seemed to be intent on getting lined up perfectly. The first quarter moon mentioned above also had something to do with the lack of stars seen in the field. (East & west reversed once more, click for a much better view).

F.G.W. Struve discovered the AB pair in 1828, and I haven’t been able to track down who added the “C” component in 1896.   S.W. Burnham would have been the most likely person, but he didn’t include it in his 1906 or 1913 catalogs, and from what I can determine, Philip Fox and George Hough didn’t measure it either.   I had hoped to get a clue from Aitken’s 1932 catalog, but for some reason he skipped over Σ 2855 entirely.

A look at the distances shown above in the next to last line of data eliminates any question as to whether the AB pair are related, since there’s approximately 385 light years separating the two.   Simbad doesn’t provide a distance for the “C” component, but there is a possibility “A” and “C” are linked physically by proper motion, as the image below shows:

Aladin image with Simbad proper motion data super-imposed. Click to enlarge!

Aladin image with Simbad proper motion data super-imposed. Click to enlarge!

Click to enlarge.

Click to enlarge.

The common motion of “A” and “C” is very obvious, and the proper motion data at the bottom of the images shows the rates of motion are very similar.   “B” is moving more rapidly, which is a function of it being much closer to us.   A look back through the recorded measures is further evidence of the relative motion of “A” and “B”, as you can see the separation (at 25.10″ in 2013) has been narrowing slowly as “B” appears to overtake “A”.   If you happen to be looking up a few thousand years from now, you’ll have the pleasure of attempting to split a very close pair of stars!

Time to go contemplate an urn of Greek olives and a glass of wine, and leave Aquarius to wend its way westward for the remainder of the year.  Our next tour will takes us north to the dense Milky Way star fields of Lacerta, where we’ll see if we can help the Lacertan lizard get a handle on his magnitudes.

Until then, Clear and Stable Skies!  😎

Another Way to Polar Align

LongRefractor1If you’ve been reading this blog for a while, you probably realize I thread my way through the night sky by star hopping.   There was a time when, like many other people, I used a Go-To mount and let it figure out how to get me to where I wanted to go.   But I soon realized I really wasn’t learning my way around the sky, which felt distinctly unsatisfying – kind of like relying on a GPS device to get you from point A to point B repeatedly without taking the time to learn the road and street signs you pass every day.   Given the fact that the skies above me are pretty darn close to magnitude six on a decent night, I decided there was no excuse for being lost most of the time when I looked up. It took a while, but I now know the constellations as well as I know my eyepieces, and there are parts of some constellations that are permanently etched into the corner of my mind reserved for maps.

But to be honest, if I was laboring under the typical light polluted urban sky, I would most likely have felt differently about the whole matter. My experience with light pollution and telescopes is limited to natural pollution, otherwise known as the full moon. It’s certainly possible to star-hop under light blasted skies, but I’ve found the typical 8×50 finder is limited to stars of about 6.0 to 6.5 magnitude when a full moon is hard at work refracting its rays all over a moisture laden sky. Under dark skies I can see stars as faint as 8.5 to 9.0 magnitude in an 8×50 finder, which makes finding my way around much less of a battle than it is when the moon is in charge of things.

If you use an equatorial mount, you quickly learned it needs to be aligned with the north or south pole in order to track an object in right ascension. If, like me, you have a motorized (tracking) EQ mount without GoTo capability, pointing it at Polaris will provide reasonably accurate tracking for most purposes.   But if you stay fixed on an object long enough, you’ll find it drifts from the center of the field of view, which requires you to use the mount’s declination controls to re-center the object.   For low-powered viewing, that’s not much of a problem.

But if the object of your attention requires high magnification, you’ll find yourself constantly re-centering it.   And if you’re trying to sketch the field of view, that perpetual wandering away from the center can make it difficult to accurately represent the stars in the field relative to each other. Which raises two questions: Why does it happen, and What do you do about it?

The answer to the first question is .75 of a degree, which is how far Polaris is from true celestial north. Which is another way of saying Polaris is really not quite the north star you thought it was. At low magnification, that .75 degree difference is minor, but with each increase in magnification, the quicker the object becomes unlatched from the center of the field. The more magnification you add, the sooner it starts to roam — somewhere around 200x you’ll see the object begin to take off almost immediately.   And if you’re a double star observer who finds 300x and 400x to be rather useful on occasion, you’ll find yourself constantly re-centering the object.

The answer to the second question – What do you do about it? – can be summed up in four words: find another north star. Or at least one closer to the actual celestial pole. As it happens, there’s a 9.65 magnitude star located a mere 13.5’ from true celestial north, which goes by several names: BD +89 38, GSC 04661-00002, SAO 3788, and TYC 4661-2-1. We’ll call it SAO 3788 since that’s the name most likely to be used to designate it.

If you’re beginning to feel a bit lost or puzzled, let’s take a look at Polaris in relation to the north celestial pole:

Stellarium screen shot with labels added, click to enlarge.

Stellarium screen shot with labels added, click to enlarge.

As you can see, Polaris is a bit shy of occupying the actual north celestial pole, which is the point at which all the lines converge.   But as you can also see, there are several stars which lie closer to the actual pole, one of which is the previously mentioned SAO 3788.

So now for the main question: how do you get to it?   You star hop to it, of course! Fortunately, we don’t have far to go, so if the idea of star hopping has you on the edge of your seat, despair not. You can do this quite easily from within the field of view of a wide angle eyepiece.

But before we get to the eyepiece view, there are a couple of things we need to pin down, the most important being the positon angle of the ninth magnitude companion of Polaris, which also serves as an important navigational tool.   In fact, we might just as well take a quick look at all the pertinent data on Polaris:

Polaris (Σ 93)  (H IV 1) (Alpha [α] Ursa Minoris)
HIP: 11767   SAO: 308
RA: 02h 31.8m  Dec: +89° 16′
Magnitudes: 2.04, 9.10
Separation: 18.10″
Position Angle: 233° (WDS 2013)
Dist: 432 Light Years
Spectral Type: “A” is F8, “B” is F3

Note the declination of +89° 16′ — further confirmation that Polaris is three-fourths of a degree short of celestial north, in case you still had doubts.

But the key number is the position angle, 233°. We’re going to use that as a reference point for determining which direction to move in order to aim ourselves towards the north celestial pole (which is at 360°). Determining celestial directions in the vicinity of the celestial pole is a very tricky business, even for the experienced observer, and it can be downright confusing when you’re gazing into an eyepiece.  The old trick of turning off your drive motor and letting a star drift across the field of view to determine which direction is west doesn’t work this close to the pole, so a navigational aid is a necessity.

Let’s start by imagining that the the line running from Polaris A through Polaris B stops at the edge of your eyepiece.   We’ll label that point 233°. When we subtract 233° from 360°, we get 127°, which is how far we need to move around the outer perimeter of the eyepiece in order to point ourselves towards celestial north.

Now we’re faced with the big question: which direction do we go? Clockwise or counterclockwise? The answer is that it depends on the kind of telescope you’re using, so pay close attention — it means the difference between success and frustration.  Assuming the use of a conventional inverting star diagonal (NOT an erect image diagonal), if you’re using a refractor or an SCT, north is clockwise from the 233° mark. If you’re using a reflecting telescope (Dobsonian, Newtonian), north is counter-clockwise from 233°. If moving by degrees around the outer perimeter of the eyepiece field is confusing, you can draw a line perpendicular (90°) to the line running between Polaris A and B and then add another 45° to that to point you toward north.

Here’s a diagram which should make all that more clear:

This may look simple when north and south are straight up and down, but that will seldom be the case when you peer into the eyepiece! Click to make the image easier to read.

This may look simple when north and south are straight up and down, but that will seldom be the case when you peer into the eyepiece! Click to make the image easier to read.

And here’s how that move looks when superimposed on our previous chart:

Stellarium screen shot with labels added, click to enlarge.

Stellarium screen shot with labels added, click to enlarge.

Now that we’re directionally oriented in the eyepiece, there’s one more thing we need to discuss before going any further, which is how to move to where we want to be. If you’re new to this, it may come as a surprise, but it’s the mount that needs to move, NOT the telescope.

When you bought your mount, the instructions for it should have covered the procedures for lining up on Polaris. The first thing you would have done is set up your mount so that the declination axis was pointing toward Polaris, and then you would have used the altitude control to move the tilt of the declination axis so that it matched your latitude – in my case, that just happens to be 45 degrees. Then you would have centered Polaris in your finder by using both the declination and azimuth (horizontal) controls on the mount, and then fine-tuned that further by making final adjustments to center Polaris in your eyepiece. During that entire procedure, you would have left the telescope untouched.

So that’s what we’re going to do here.

With the counterweight shaft pointing straight up and down, and the declination circle lined up with the ninety degree mark, lock the declination and right ascension clutches on the mount and then use the altitude and azimuth controls to center Polaris, first in your finder, and then in your eyepiece (if your mount has locks for the altitude and azimuth controls, make sure to unlock them now – and don’t forget to lock them when we’re done!). Here are photos of two frequently used equatorial mounts, which will give you an idea of what to look for in the way of altitude and azimuth controls:

This is a Celestron CG4 mount. The altitude and azimuth controls are unlocked when one of the control devices is loosened, and locked when the two opposite devices are turned so they're pressed against one another. Other mounts, such as the CG5, have similar controls. Click for a larger view.

This is a Celestron CG4 mount. The altitude and azimuth controls are unlocked when one of the pairs of control devices is loosened, and locked when the two opposing devices are turned so they’re pressed tightly against one another. Other mounts, such as the CG5, have similar controls. Click for a larger view.

 

To unlock the azimuth and altitude controls on the Losmandy G11, just loosen the wing nuts shown in the photo -- note there are two, one each on opposite sides of the mount. The Losmandy G8 uses the same setup. Click for a larger view!

To unlock the azimuth and altitude controls on the Losmandy G11, just loosen the wing nuts shown in the photo — note there are two, one each on opposite sides of the mount. The Losmandy G8 uses the same setup. Click for a larger view!

All the movements we’re going to make from this point forward will be made using the altitude and azimuth controls on the mount.

Now if you look carefully at the chart above (here it is again), you’ll see there’s actually an easy way to star hop to SAO 3788. Notice that the Polaris A-B line points almost directly at 6.45 magnitude HIP 7283, which is distinctive because it’s bright and because of the ninth magnitude star located next to it (that star has a name by the way, SAO 223).   And if you move towards true celestial north from HIP 7283, you’ll see it leads you past 8.10 magnitude HIP 3128. And if you extend that line an equal distance, it just happens to lead you to our goal, 9.65 magnitude SAO 3788.

And here’s how that looks when diagrammed, minus the celestial grid in our previous chart:

Stellarium screen image with labels added. (Both this and the previous image portray the scene as it would be seen in a refractor or SCT, meaning east and west have been swapped).

Stellarium screen image with labels added. (Both this and the previous image portray the scene as it would be seen in a refractor or SCT, meaning east and west have been swapped).

Here are those moves once more, but this time plotted on our earlier grid:

Stellarium screen image again, click to enlarge.

Stellarium screen image again, click to enlarge.

So how does all that look in the eyepiece?

Click to enlarge – note, east and west are reversed here to match a refractor or SCT view.

Click to enlarge – note, east and west are reversed here to match a refractor or SCT view.

This is the view with a 40mm Celestron Plössl in a 9.25 inch SCT. I’ve moved Polaris to the eastern corner of the field in order to pull HIP 7283 and HIP 3128 into the field of view.

If you now move toward the north until HIP 3128 is in the same position in the eyepiece as HIP 7283 was, you’ll see our goal, SAO 3788, come into view at the opposite (north) corner of the field of view:

Click to enlarge!

Click to enlarge!

Center SAO 3788 in your eyepiece and you’re now a mere 13.5’ from true celestial north.   Once you’ve done this a few times, you’ll find it’s quick and easy to do.

I’ve found parking SAO 3788 in the center of my eyepiece is more than sufficient for a 400x view — I can barely detect any motion unless I stay on the object for ten minutes or so. Remember, we’ve gone from being 44’ off center from celestial north to 13.5’, which is a huge improvement.

Lock up your altitude and azimuth controls, unlock the declination and right ascension clutches, grab a 4mm eyepiece, and go split that pair of sub-arcsecond stars that’s been on your list for the past year without having to chase it across the field of view!

Happy star hopping and clear skies!