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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! 😎

Touring the 50mm/60mm Skies, Tour Number Three: Cepheus

OK, if I tormented your tolerance for the difficult on the last tour, I positively promise I’ll do better on this one.  We’re going to cut a swath of ease from one corner of Cepheus to the other, and then to top it all off, we’ll linger over the rare beauty to be found on its southern fringes, near the Cygnus border.

First, though, you need to meet the individual that made this tour possible, the Cephean King:

I do believe that’s an old 40mm long focal length refractor the King is holding there in his left hand, and it even looks like the Lacertan Lizard is attempting to get a look into it.  And for baseball fans, if you look closely at the constellation’s outline which is superimposed on the king, it’s remarkable how much it looks like home plate.  And it can serve as a pointer to Polaris as well — if you follow it north, it’ll take you ten degrees west of the North Star.  (Stellarium screen image with a few labels added and ….. er …… a few modifications; click for a closer look).

We’re going to start just below the King’s right elbow, where we’ll find Beta (β) Cephei, which was also known as Alfirk back in the days of the Arabian astronomers.  So grab your scope and let’s head out the door!  (If you missed it, the background on the scopes and eyepieces we’re using in this series can be found here).

You’ll find 3.2 magnitude Beta (β) Cephei shining somewhere between fairly bright and almost dim in the northwest corner of the slightly warped Cephean square, and we’ll meet its partners in duplicity, Xi (ξ) and Delta (δ), as we work diagonally across to its southeast corner. Note that this chart has been rotated ninety degrees to the right in order to match Cepheus’ position in the early evening winter sky. (Stellarium screen image with labels added, click to enlarge).

Beta (β) Cephei  (Σ 2806)  (H III 6)          HIP: 106032    SAO: 10057
RA: 21h 28.7m   Dec: +70° 34′
Magnitudes:  3.2, 8.6
Separation:  14.4″
Position Angle:  251°   (WDS 2011)
Distance: 595 Light Years
Spectral Classification: B2, A
Rating: Easy to moderate

Greg first called my attention to Beta (β) about a year and a half ago, and since then I’ve looked at it more times than I can remember.  I’ve always been delighted to have its white light warm the innards of a 60mm refractor, and it was no different this time for the 60mm f/13.3 I’m using for this series.  The temperature was about thirty five degrees on this cool winter evening, with a cold breeze out of the north rattling some dry leaves across the ground under my deck — even the winter weather adapted 50mm Zeiss saluted Beta’s warm white light with a hearty “Vielen Dank!”

I started with low magnification in both scopes — the 20mm Televue Plössl (40x) in the 60mm scope and the 15mm TV Plössl (36x) in the Zeiss 50mm.  Although the two stars are separated by a modest 14.1″, there’s slightly more than five magnitudes of difference between them  — which means you gotta look closely to see the secondary!

I did, and it was clearly there, nestled up snugly to the primary, which looked like the smart thing to do on this cold winter evening.  That secondary is a very tiny, grayish-white gleaming point of light, and considering that it’s a mere 8.6 magnitude collection of photons, it’s surprisingly intense.

Look closely or you’ll miss that dim little secondary — and then be prepared to slip into a primary stupor. (East & west reversed to match the refractor view, click for a larger look).

But it was the primary’s white that wowed me into a stupor.  You have to see this on a moonless night!  As you center it in the eyepiece and bring it into focus, it locks your eyes in its embrace before you even think about resistance.  I’ve mentioned the delicate quality of the 60mm view of Beta (β) in a previous description of it, but there wasn’t anything delicate about this process.  It grabbed me and refused to let go.  Not that I put up a lot of fight, mind you.

The highlight, though, was the hypnotic view created by the combination of the 50mm Zeiss and an 11mm TV Plössl.  Now that’s only a 49x view, but it’s the best 49 x’s I’ve had for quite some time.   I experimented with the 7.5mm Celestron Plössl in both scopes a few times, and since the 50mm/11mm combination kept calling me back, I decided to use it for the accompanying sketch.

Although this is not a difficult pair to pry apart, I’ll throw in a moderately difficult rating for Beta (β), if only because you have to sit up straight and give it your undivided attention in order to see the secondary.  But it’s really not much strain, and it more than rewards the minor effort required.

Not at all a bad start for this third tour!

Now we’ll start our diagonal trek across the center of Cepheus to our next stop, Xi (ξ) Cephei, which also has another name from its Arabian past, Kurhah.

Xi (ξ) Cephei  (Σ 2863)  (H II 16)           HIP: 108917    SAO: 19827
RA: 22h 03.8m   Dec: +64° 38′
Magnitudes: 4.5, 6.4
Separation:  8.36″
Position Angle: 274°   (WDS 2012)
Distance: 102 Light Years
Spectral Classification: A3, F7
Rating: Easy

This is another easy assignment for both scopes tonight, although you’ll discover you do have to look closely once again to distinguish the glow of the secondary.  If you’ve been using larger aperture scopes, and this is your first foray into the night sky with a 50mm or 60mm refractor, one of the things that will strike you immediately is the delicate appearance of the stars.  That delicacy is created by the smaller, tighter appearing points of starlight, but it also requires closer scrutiny when separating closely spaced pairs.  Once you get used to the difference, it’s not at all difficult, and in fact, adds considerably to the aesthetic charm of the view.

As you bring Xi (ξ) into focus, you’ll see it sports a bit of color — unlike Beta (β) — which is very evident even in a 50mm or 60mm lens.

A soft gold primary and a silver-white secondary combine to give Xi (ξ) an elegant distinction. (East & west reversed again, click for a more distinct view).

That color — it’s a pleasantly light gold — was the first thing that captured my attention.  So much so, in fact, that I almost had to force my eyes to search for the secondary, which is about twice as close to the primary as what Beta’s was.  In this case, though, we’re only dealing with a two magnitude difference in brightness, as compared to 5.4 magnitudes of difference between the Beta (β) pair.  To put numbers to it, what that means is Beta “B” is about 150 times fainter than Beta “A”, while the Xi (ξ) secondary is a mere 6 times fainter than its parental primary.  And because it’s brighter, that secondary appears to ours eyes to be noticeably larger than Beta’s secondary — which provides the added benefit of making it easier to pick out of the primarial glow.

One strange thing about that color, though — and star colors are notoriously unpredictable — is that with a classification of A3, the primary should appear white.  And the secondary, classed at F7 (which is almost into the yellow category — see this chart), should be the one that appears to be yellow — but I saw it as white.  I can’t help but wonder whether that secondarial color eked its way over to the primary instead.  Who knows — it’s just as likely to be the reverse the next time I look.  It certainly wouldn’t be the first time!

Don’t hesitate to add some magnification here since both of these stellar lights emit more than enough light to keep your eyepieces illuminated.  I switched back and forth several times in both scopes from the low magnifcation-wide field view offered in the 20mm TV Plössl to the more restricted confines of the 7.5mm Celestron Plössl, but finally found the 20mm (27x) view in the Zeiss to be the most attractive.

That combination provided a luxurious two degree field of black velvet for a backdrop, and it placed the Xi (ξ) pair so close together they were barely apart, yet still clearly separated with distinction.  Adding to the sheer charm of the view was the circular black void that surrounds them.  The nearest clustering of stars bright enough to attract your attention is at the southeast edge of the eyepiece field.

In that sense, Xi (ξ) is in full command of its immediate surroundings — because if you pan around the field a bit, or peek into a 6×30 or 8×50 finder, you’ll find this double delight is actually located in a very rich field of sparkling white diamonds.  Take a look around — it’s a beautiful sector of the galaxy!  It would be a shame to race right past it to Delta (δ) without pausing to explore for a few minutes.

Delta (δ) Cephei  (Σ I 58)  (H V 4)           HIP: 110991    SAO: 34508
RA: 22h 29.2m   Dec: +58° 25′
Magnitude:  4.2, 6.1
Separation: 41.1″
Position Angle: 191°   (WDS 2011)
Distance: 983 Light Years
Spectral Classification: F5, B7
Rating: Easy

Now if you look again at the chart we’re using, you’ll see Delta (δ) lurking off of the eastern edge of the slightly out of kilter Cephean square.  If you can’t quite see it, extend a line from Xi (ξ) to Zeta (ζ), and then make a ninety degree turn to the east and you’ll land practically on top of it.

Delta (δ) actually deserves a rating of easier than easy.  There’s nothing difficult here — in fact, it rolls over and surrenders its duplicity without the least fight on first sight.  And it’s Albirean beauty is immediately captivating.

If we’ve followed a progression here in level of difficulty from moderately easy to easier than easy, we’ve also followed one of color.  Beta (β) was all white — fantastically white — Xi (ξ) showed us a bit of gold, and Delta (δ) simply steals the show.

Shades of Albireo! Weaker in intensity — although not by much — this pair of stars could almost be mistaken for that more famous gold and blue pair in Cygnus. (East & west reversed once again, click to get a better view — and turn out the lights! It makes a difference!)

Its 4.2 magnitude primary is a glowing little globe of gold-yellow-white light, accompanied at a comfortable distance by a slightly blue secondary of two magnitudes less intensity.  They put on one of the best imitations of Albireo that you’re going to find high over your head.  If you could turn up their brightness levels to match those of Albireo, I would wager a pair of Plössls you would find yourself looking at identical twins.

The wide field view is still the best here, but don’t hesitate to increase the “X” factor.  I saw some of the star color start to fade in the 60mm scope using the 11mm TV Plössl (73x), and also in the 50mm Zeiss loaded with the 7.5mm Celestron Plössl (72x).  But in compensation for the slight loss in color, that little group of three stars just to the west of the Delta (δ) pair emerged in a different light, putting on a display of distinctive character that had me wondering if they might be stellar relatives.  And not surprisingly, that turns out to be the case.  In fact, it’s a triple star, but only two of the three components are visible in the sketch.

This is a complicated star that carries two designations.  What you see in the sketch is the AC pair, designated as ARN 79, with magnitudes of 8.5 and 9.5, separated by 79.2″, with a position angle of 320 degrees (WDS 2008).  What you don’t see is the “B” component, designated as H 4 31 — that secondary has a magnitude of 10.5 and lies 25.3″ from the primary, at a PA of four degrees (WDS 2008).  I’ll un-officially designate them now with another name — the Deltarian Guards — since they seem to be doing just that.  And I’ll add that the AC pair is an easy split in either the 50mm or the 60mm scopes.

What I had originally planned to do next was lead you over to Mu (μ) Cygni, also known as Herschel’s Garnet Star.   No, it’s not a double, but it’s radiates one of the purest, deepest, head-turning shades of deep orange and/or red in the Celestial Sphere.  Sir William obviously saw the color as garnet, and thus the name.  You can find that garnet glow lying about a degree south of and halfway between the line that connects Zeta (ζ) Cephei and Alpha (α) Cephei, as shown in the chart below.  This is a variable star, fluctuating between 3.6 and 5.0, but regardless of what magnitude you happen to catch it at, it’s a beautiful sight in a medium focal length eyepiece — say the 15mm TV Plössl — in the diagonal of a 60mm scope.

But — as I was being enriched with Mu’s dark orange-red photons, my memory circuits re-connected and reminded me there just happens to be a pair of stars lying nearby, one of  which is quite a sight in a 60mm lens.  So we better take a peek — or we’ll both regret it forever.

And it’s not at all hard to get there:

Mu (μ) Cephei sits a degree south of the line joining Alderamin, aka Alpha (α) Cephei, and Zeta (ζ) Cephei. Our next two stars, Σ 2816 and Σ 2819, are enveloped in the reddish glow about another degree to the south, which goes by the name of IC 1396. (Sky Safari screen shot with labels added, click for a larger look).

Σ 2816  (H III 71)         HIP: 106886    SAO: 33626
RA: 21h 39.0m   Dec: +57 29′
Magnitudes   AC: 5.7, 7.5    AD: 5.7, 7.5
Separations   AC: 11.8″       AD: 20.0″
Position Angles   AC: 120°  AD: 339°    (WDS 2010)
Distance: 1173 Light Years
Spectral Classification: O6
Rating: Easy

Σ 2819  (H III 72)  (No HIP or SAO numbers assigned, use those for  Σ 2816)
RA: 21h 40.4m   Dec: +57° 35′
Magnitudes:  7.4, 8.6
Separation:  12.7″
Position Angle:  59°   (WDS 2003)
Distance: 245 Light Years
Spectral Classification: F5
Rating: Moderate

Now it’s Σ 2816 that I want to call your attention to — not that I need to, because you’ll find your eyes are drawn to it so quickly you can hear them snap into place.  It’s bright white 5.7 magnitude primary has two evenly matched 7.5 magnitude companions arrayed on either side of it, forming an open “V” pattern, almost like the wings of a bird in flight.

I found the triple impact of Σ 2816 so stunning it took a few minutes to absorb it all. There is a lot to be seen in this one degree field of view. Absorb it slowly — let time stand still for a while. (East & west reversed, click to get a larger look).

To it’s northeast, you’ll see the 7.4 magnitude primary of Σ 2819, and you’ll have to look closely to catch the 8.6 magnitude hint of its secondary, somewhat obscured by the glow created by the 1.2 magnitudes of difference.

In between these two stars is another close pair which also lays claim to a shared stellar lineage.  That one is STI 2582, which according to the most recent figures in the WDS (2002), has magnitudes of 8.0 and 11.1 separated by by 21.1″ at a position angle of 187 degrees.  I’m rather surprised I captured that faint secondary in the Zeiss 50mm refractor, but the transparency that night was excellent, and it allowed me to go a bit deeper than I would have otherwise.

So in a one degree field of view, we have a beautiful triple star, a somewhat challenging double, and another pair that’s even fainter and more challenging  —-  and all of it well within the reach of lenses of fifty or sixty millimeters in diameter.

And that’s not all!  If you happen to be looking at these two stars on a dark night with good transparency — and your eyes are totally adapted to the darkness — you’ll see thin wisps of nebulosity scattered here and there through the field of view — yes, even in these small apertures .

It’s best seen at low magnification, so stick with the 20mm view in the 60mm scope, and use the 20mm or the 15mm eyepiece in the 50mm scope.  That nebulosity, designated IC 1396, belongs to the red glow which can be seen on the chart shown above.  This area is also considered an open cluster, and again, it’s cluster-ness is best seen at low magnifications.

But for the best view of the Σ 2816/Σ 2819 pair, I found the 15mm Plössl (53x) was my first choice in the 60mm scope, and the 11mm Plössl (49x) came out on top in the 50mm scope.  I started a sketch using the 60mm scope on the same night I made the sketches for the three Cephean stars already described above, but the clouds took command of the sky before I got very far.  So I went back two nights later and used the 50mm Zeiss/11mm TV Plössl combination.

The seeing was poor, poor, poor, and sometimes horrible, horrible, horrible — which meant I found myself adjusting the focus several times to bring out the background stars.  But in the stunning transparency that was at the opposite side of the seeing scale, the nebulosity of IC 1396 really wrestled my attention away from these stars.  In fact, I was thrilled to the tips of my focus fingers with the fact that I could see it so clearly in a 50mm lens.

My advice is to linger here for another hour or so and just scan the sky slowly.  This is a rich section of the Milky Way — start at Mu (μ) Cephei and gradually work your way into the northern Cygnus area and you’ll be amazed at what you can see.  If you can latch onto a leisurely pace, you’ll find yourself looking at more starry clusters than you can count, and immersed so deeply in nebulosity you’ll never find your way back to Mu (μ).  But since we’re done for the night now, go ahead and get lost up here!

And by the time you find your way home, we should be just about ready for the next tour.  For that one we’ll traverse to the opposite side of the cinematic celestial screen and ferret out four new and seldom seen doubles in Taurus.  So don’t disappear — Tour Number Four will soon appear here!

Cephean Siblings: Σ2840, OΣ 480, OΣ 486, Σ2872, and S800

Sometimes it’s amazing what you can find in a small area.  Greg and I have hit all the double star highlights in Cepheus – I think – but there are a whole more in this constellation that merit at least a look.  You’re not going to jump up and down and holler loud enough to wake up the neighbors at 3AM — if you do, leave me out of it, please — but if you approach this as an exercise in sharpening your star-hopping skills, you should be pleased with what you find.  Don’t expect a riot of color in any of these, but do expect to hone the subtle sensitivities of your visual apparatus.  🙂

Stellarium screen image with labels added, showing the locations of all the stars on our tour. Click on this or any of the other images for a larger view, and then a second time to enlarge it once again.

We’re going to use Delta (δ) Cephei as a base, because it’s easy to find and is centrally located in relation to these stars.  If you haven’t looked at this star, spend some time taking in the beautiful reddish-orange of the primary and the delicate blue of the secondary.  When you’ve done that,  we’ll get started by hopping off to the southwest.

Chart 1, showing Σ 2840 and Σ 2872. (Stellarium screen image)

Σ 2840  (H IV 79)         HIP: 107930    SAO: 33819
RA: 21h 52.0m   Dec: +55° 48′
Magnitudes: 5.6, 6.4
Separation:  18.1″
Position Angle: 196°  (WDS 2011)
Distance: 643 Light Years
Spectral Classification: B6
Status: The 5.6 magnitude “A” component is a spectroscopic binary

October 3rd, 1 AM:    This eye-pleasing double lies about five degrees (the average width of an 8×50 finder) to the southwest of Delta (δ).  If you’re star hopping — and I hope you are, you’ll never learn where things REALLY are any other way! 😉 —  move a distance of two degrees from Delta (δ) to Epsilon (ε) Cephei, and then continue another three degrees to the southwest and Σ 2840 will come into view in the finder.

Σ 2840 (STScI photo)

This pair lies in a rich star field, but when viewed through the eyepiece of a telescope, you’ll find them surrounded mainly by blackness, which has the wonderful effect of drawing your eye right to them.

Using my 60mm f/16.7 refractor and a 25mm Plössl (40x), I could see two white dots, one slightly brighter and larger than the other.  I took a look at it also in my Antares 105mm f/14.3 refractor with an 18mm Radian (83x), but found I preferred the view in the smaller scope — to my eyes the two stars are just more satisfying when seen closer together.   Not sure what that says about my eyes or taste — but I’m stuck with my eyes, and there’s no accounting for taste.

OΣ 480 Cephei (STT 480)   (No HIP assigned)     SAO: 34785
RA: 22h 46.1m   Dec: +58° 04′
Magnitudes: 7.6, 8.6
Separation:  30.6″
Position Angle: 117°  (WDS 2010)
Distance:  ?????
Spectral Classification: F8

Chart 2, showing OΣ 480 and OΣ 486 (Stellarium screen image)

October 3rd, 1:30 AM:     Now return to Delta (δ) Cephei and prepare to move east.  About one degree to the east of Delta (δ) you’ll see a line of three almost evenly spaced seventh magnitude stars running from the northeast to the southwest.  Center the middle one in your finder, then move another degree east and you’ll see two sixth magnitude stars lying at the same angle.  Center the southern-most of the two, and you’ll see OΣ 480 lying to the southeast, right at the western edge of a cluster of stars.

These are perfect for a 60mm scope – I used a 26mm Plössl for 39x and found two easily separated stars, one a bit brighter than the other, staring back at me.  Haas describes them as “lemon white, azure white,” but they were really too faint for me to describe them as anything other than a faint white.

OΣ 480 (STScI photo)

These two stars lie right at the edge of an open cluster, NGC 7380, which is slightly oval in shape.  I counted about twenty stars in my 105mm scope using an 18mm Radian (83x).  There is an area of nebulosity, SH2-142, associated with this cluster, which was easily seen in both the 105mm and the 60mm scopes.  I was enjoying a moonless night with excellent transparency, but was still surprised by how well the nebulosity could be seen in the 60mm scope at 39x.  The Night Sky Observer’s Guide comments that an OIII filter really isn’t necessary to see the nebulosity — and obviously, they’re correct!

This is heaven — a few wisps of nebulous clouds entwined in a small cluster of stars, with a small pair of pinpoint sharp, white stars at the edge.  I had to restrain myself from waking up the neighbors.

OΣ 486         HIP: 113853    SAO: 20393
RA: 23h 03.4m   Dec: 60° 26.7′
Magnitudes: 6.7, 9.5
Separation:  35.2″
Position Angle: 276°  (WDS 2006)
Distance:  1930 Light Years
Spectral Classification: B2
Status: The 6.7 magnitude “A” component is a spectroscopic binary

October 10th, 12:30 AM:     Now, don’t move your scope yet! – even though I did. To get to our next pair, we’re going to start from OΣ 480 (see chart number two above) and move one degree northeast to a triangle of seventh and eighth magnitude stars.  From there, continue another two degrees along that same line and OΣ 486 should be the brightest star near the center of your finder.

OΣ 486 (STScI photo)

This is a fairly wide pair and easy to split.  I could see the faint 9.3 magnitude companion in the 105mm scope using an 18mm Radian (83x) with no problem, but I needed to use averted vision in the 60mm equipped with a 17mm Plössl (59x) to detect it.  It lacks the added interest of being right at the edge of an open cluster, as was the case with our previous pair, OΣ 480.  However, NGC 7510 lies a bit less than a degree to the northeast, so if you’re using an eyepiece with a field of view of about one and half degrees, you should see it at the edge of your eyepiece while OΣ 486 is centered in it.  It’s a tight little cluster of about four arc minutes in diameter which is listed at a magnitude of eight, so don’t expect to see the Pleiades!   I could resolve about a dozen stars in the 105mm at 83x, with the fainter members adding a nebulous glow to the background.

Σ 2872 (22 Cephei)  (H IV 126)    (No HIP number assigned)     SAO: 34101
RA: 22h 09m   Dec: +59° 17′
Magnitudes: 7.1, 8.0
Separation:  21.7″
Position Angle: 316°  (WDS 2008)
Distance: ?????
Spectral Classification:  B9.5

October 10th, 1AM:     OK – back to Delta (δ) again on chart number one above!  We’ll start by moving two degrees west to Zeta (ζ) Cephei (also known as 21 Cephei) and then one degree north — with a slight bias to the west — and you should have Σ 2872 in your finder, with the brighter fifth magnitude Lambda (λ) Cephei lying just to the east of it.

In the 60mm scope using a 26mm Plössl (39x), I found two white dots very close to each other, one barely brighter than the other.

Σ 2872 (22 Cephei) (STScI photo)

A  17mm Plössl (59x) separated them just far enough to make a very attractive pair.  Switching to the 105mm refractor, an 18mm Radian (83x) gave me a view similar to that in the 60mm at 59x, but significantly brighter.

This pair is located in a rich star field, but as was the case with our first pair of doubles, Σ 2840, the view in the eyepiece reveals the immediate area surrounding them to be almost devoid of stars.  If you move your scope about 3/4 of a degree (45 arc minutes) to the northwest, the beautiful and very interesting quintuple star OΣ 461 (15 Cephei) will come into view.

S 800         HIP: 108073    SAO: 19718
RA: 21h 53.8m   Dec: 62° 37′
Magnitudes: 7.1, 7.9
Separation:  62.6″
Position Angle:  145°  (WDS 1999)
Distance:  2346.5 Light Years
Spectral Classification:  B1

Chart number 3, showing S 800 (Stellarium screen image)

October 10th, 1:30 AM:     And now for something completely different — a new starting point!   I got lost more than once trying to find this one until I finally got smart and decided to search for it by starting instead at 4th magnitude Xi (ξ) Cephei, which lies almost right in the middle of the rectangular shape formed by Alpha (α), Beta (β), Iota (ι), and Zeta (ζ) Cephei  (see the chart at the beginning of this tour).

S 800 is located two degrees to the southwest of Xi (ξ), but the easiest way to get there is to first move directly south 1.5 degrees.  This will bring you to a north-south line of three fifth magnitude stars, which are 18, 20, and 19 Cephei, in that order.  Center your finder on the middle one, 20 Cephei, (it should already by pretty close) and move west one degree and you’re there.

S 800 – NGC 7160 (STScI photo)

Now what we have this time is a double star right in the middle of a small open cluster, NGC 7160, measuring about six minutes in diameter — and in the 105mm scope that’s exactly what it looks like – but no nebulosity this time.  In addition to the two stars of S 800, there is a faint pair of 10th magnitude stars slightly to the northeast and a trio of ninth magnitude stars to the southwest, which are the brighter members of this faint cluster.

S 800 is a tight pair in the 60mm scope at 39x using a 26mm Plössl, but is much improved after moving up to a 17mm Plössl (59x), and is a very pleasant sight in the 105mm scope using a 14mm Radian (107x).  Haas describes them as “pure-white and green-white” – I agree with the white, but couldn’t detect the green.

And now, if you’ve done all this in one night, sit back and take a break, and think about what you’ve seen — five pairs of double stars, three of them located at the edge, or not far from, or in the middle of open clusters, and two completely surrounded by almost nothing but black space.  And even though we’ve stayed within a square of about eight degrees of dark sky, we’re stuck out here at S 800, a distance of just over 2346 light years from home.  So you should be tired!

And if you’re not, you sure will be by the time you get there.   😎

Delta (δ) Cephei: A Lighthouse in the Sky

Delta (δ) Cephei  (Σ I 58)  (H V 4)          HIP: 110991    SAO: 34508
RA: 22h 29.2m   Dec: +58° 25′
Magnitude (AC):  4.2, 6.1
Separation (AC): 40.6″
Position Angle (AC): 191°   (WDS 2012)
Distance:  983 Light Years
Spectral Classification: F5, B7
Status:  “C” is variable and a spectroscopic binary

Greg and I have roamed all over Cepheus and somehow both of us missed the chance to write about this colorful gem.  Not only is it one of the more colorful doubles in the sky, but the primary is also one of the most famous.  My first good look at it was in a Meade AR-5 (127mm, f/9.3) and my 90mm Orion f/10.1 on a chilly, moonless night.  This is a beautiful pair of widely separated stars — in fact, the companion described here, “C”,  actually lies 12,000 astronomical units from the primary!

Screen shot from Stellarium; click on image for a larger view. (Delta (δ) Cephei can be seen at the top left).

First, the colors.

In the two scopes mentioned above, the primary is a rich yellow with a tinge of red to it, and “C”  is a pronounced blue color, leaning a bit toward white.  Haas has them as “citrus orange and royal blue,” and considers them a showcase double – which they certainly are.

Even in a 50mm refractor, this is a colorful pair! Click to get a closer view.

Delta Cephei, with triangular asterism at its west edge. Click on image for a larger view. (STScI photo)

I was eager to get another look at this pair on the next clear night.  The weather being fickle once again, it was another five nights before I got the chance.  This time I was using a 105mm Antares f/14.3 and a 60mm f/16.7.  Maybe it was the scopes, maybe something in the atmosphere, or maybe just me, but I noticed the red tint was more noticeable in the primary and there seemed to be less white in “C”.  Both times my eye was drawn to an interesting trio of eight and ninth magnitude stars to the west which contributed a little something extra to the scene.

Now, for the famous part.

Surprisingly, Delta Ceph has never been graced with a name, but it certainly deserves one.  It has given the name of the constellation it resides in to an entire class of variable stars, Cepheids, which are used to determine stellar and galactic distances.  The luminosity of these stars is directly related to their periods of variability, which are very consistent.  Delta Ceph ranges in magnitude from 3.5 to 4.3 over a period of 5 days, 8 hours, 47 minutes, and 32 seconds, and it’s 2000 times more luminous than our sun.  It’s classified as a super-giant, as well it should be, with a diameter forty times that of the sun.

So how do you use a star to measure distances?  Surprisingly, it’s not all that complicated.

The period of variability of a Cepheid provides the luminosity, which is the intrinsic brightness of the star measured in relation to our sun.  The longer the period of variability is, the more luminous the star.   With the star’s luminosity pinned down, its visual magnitude as we view it from earth provides us with its distance.  Like a 100 watt light bulb seen at a distance, the star’s visual brightness as seen from earth is related to how far away the light source is.  Based on this characteristic, Cepheids, like lighthouses and 100 watt bulbs, can be used to provide very reliable distance measurements.  We owe the discovery of  this luminosity-distance relationship to Henrietta Levitt, which was established in 1912 based on her observations of Cepheids in the Small Magellanic Cloud.  A good discussion of her role can be found in Marcia Bartusiaks’ The Day we Found the Universe or in Timothy Ferris’s The Red Limit.

Because they are very luminous, Cepheids can be seen in other galaxies with large telescopes.  Once identified, they can then be used to measure the distance to the galaxy in which they are found.  It was Edmund Hubble‘s discovery in 1923 of a Cepheid in the Andromeda “nebula” (M31) which, when combined with additional observations throughout 1924, allowed him to establish that it lies far beyond the Milky Way.  That put to rest an early twentieth century debate as to whether Andromeda was a nebulous cloud residing in our galaxy or whether it was a galaxy residing outside of our own, thus providing astronomers with the first definitive indication that an entire universe existed beyond the Milky Way.  At first, telescope size limited the detection of Cepheids to nearby galaxies, but the Hubble scope and earth-bound telescopes using adaptive optics have been able to extend the distance at which Cepheids can be detected far beyond the earlier limitations.  Other methods are also now used to determine galactic distances, but Cepheids are the foundation on which most all methods rest.

So when you’re sitting there at the eyepiece of your telescope enjoying the rich yellow and bright blue colors of Delta (δ), think of it as a window into the true dimensions of our universe.

And getting back to the lack of a name, I’ve always felt that Henrietta Levitt deserves more recognition for her work on Cepheids.  So, I lean toward Levittania as a good name for Delta Ceph.

Observations of Delta Cephei were made on September 28th and October 3rd, 2010, under dark, moonless, relatively transparent skies with seeing wavering between pretty poor and pretty awful.

Information on Delta Ceph is from Jim Kaler’s site; information on Cepheids comes from the two books mentioned above.

(WDS data updated 6/22/2014)

OΣ 461 (STT 461) Cephei, a Quintuple System, and a 4AM Walk in the Moonlight

OΣ 461  (STT 461)               HIP: 108925    SAO: 34016
RA: 22h 03.9m   Dec: 59° 49′
Magnitudes       Separation          PA                               Spectral Classification
AB:    6.7, 11.4        11.10″            297°  (WDS 2011)                      B1
AC:    6.7,10.0        88.90″              49°  (WDS 2011)                      B1, K0
AD:    6.7,  7.8      184.30″              72°   (WDS 2011)                     B9
AE:    6.7,  7.0       237.40″              37°  (WDS 2011)                     B9
DE    7.8,  7.0       136.10″            346°  (WDS 2003)                     A
Distance: 1371 Light Years
(WDS numbers updated 7/28/2013)

2 Am, September 3rd, 2010

After being introduced by Greg to the beautiful double/triple combination of Σ 2816 and Σ 2819 in Cepheus, I’ve gone back several times to take another look at them, as well as Herschel’s Garnet Star, which is a piercing deep red.  Against the background of a very black sky, it’s one of the most stunning objects in the heavens.  I could spend a week of nights in this area of Cepheus and probably still not have enough time to appreciate all there is to see here.

This is where we are this morning. Click on image for a larger view, and then click again when the image comes up on your screen. Screen image from Stellarium with labels added.

About four to five degrees to the east of the Garnet Star is the very rare five star system 461.    (Greg has also covered this system here).  In the eyepiece it looks like an open cluster, but the remarkable thing about it is the colors – all white – and the line of three seventh magnitude stars arrayed at almost equal distances from each other.

But, it takes some effort to pin down the positions of all of the components of this one.

Quintuple system in Cepheus. “B” is almost hidden here in the glare of “A” – click on image to see it more clearly, and then click a second time. STScI photo, labels added.

“A”  is the brightest of the bunch, and it dominates at one end of the system.  “B” requires a decent aperture to be seen because it is relatively close and 5.2 magnitudes dimmer than the primary.  I’ve had no problems picking it out of the glare with 105mm and 152mm refractors, but it does a good job of staying hidden in a 60mm refractor.  “C” is the second dimmest of the stars in this sytem and is easy to identify to the northeast of the primary because it sits out there all by itself.  “D” is east of it at twice the distance from the primary, and again is off in an area by itself.    “E” is the farthest out, just to the north of “D.”  Apparently the last star in the line, to the northeast of “E,” is not related to this system.  And, as the “DE” designation indicates, these two stars are also gravitationally linked.  So we have a quintuple star system with a double system imbedded in it.

By 3 AM  the seeing was deteriorating quickly.  At the same time, though, the transparency was improving rapidly.  I could see the sky had become a bit brighter as a waning crescent moon rose over in the northeast, although it was hidden from my view by the trees.  Even with the additional light, though, the sky was as crisp, clear, and sharp as I’ve seen it.  I swung my 105mm refractor over to M33 and had a splendid view with a 40mm eyepiece. But the real surprise was M33 in the 60mm f/15 scope.  With a 32mm eyepiece, it really stood out well from the background despite the slightly brighter sky.  The oval shape could be clearly seen, a few stars in the center of the galaxy were twinkling, and a nebulous area that is one of the spiral arms could just be seen stretching out to the east.  Never under-estimate what great transparency can do for a small telescope.

Usually when I finish for the night, or morning, I take my four-legged companion for a short walk.  There is an area one block over and to the north of my house that has an almost unobstructed view stretching from west to north to east.  I decided that was a good place to be on this morning, and as I came around the corner into the clearing, the crescent moon stood about twenty degrees above the tree line.  There was magic in this view.

To the right of it, the “V” shape of Taurus was parked in a horizontal position pointing into the heart of Auriga, Aldebaran and Capella twinkling rapidly.  Above the tree line and to the moon’s left, the Gemini twins were stretched out on their side, one foot pointed up into the sky, the other hidden in the trees.  Castor twinkled brilliantly at the head of one of the twins and Pollux could just be seen below it shining through the hemlocks and cedars.

And then there was Orion, truly a majestic sight if ever there is one.  It was up high enough that the belt and the glowing nebula below it could be seen above the trees.  When I see the huge outline of Orion rising above the trees, tilted at a forty-five degree angle, with dark red Betelgeuse shining intently and the three stars in the belt pointing up into the sky, I am always left “rapt in awe” — always.

I stood there for a good thirty minutes in the peace and quiet.  Not a soul anywhere to be seen, not a car to be heard.  The temperature was about 50 degrees, and I could feel a slight breeze on my face – cool, damp, and soothing.  Just me, Klaus, a beautifully transparent sky, a few constellations and twinkling stars, the moon, and that very dark, very deep blue sky.  Words don’t really describe this.  It was something you feel, something that penetrates to your very core, something you don’t want to leave, something you don’t ever want to not be a part of.

As I said, magic.

Klaus

Omicron (ο) Cephei, Σ 2883 (STF 2883), and Σ 2923 (STF 2923)

August 23rd, 2010, just after midnight

Fall is in the air again tonight – already the temperature is a crisp fifty-one degrees.  Adding to the autumn ambience is a very bright moon in the southeastern sky which is just a few hours away from being full, so this will be a night for turning the scopes to the north to do some exploring in Cepheus.

Sears 80mm on the left, Mizar-Carton 80mm on the right.

And I’m going to do something I’ve been wanting to do for a while, which is to mount a pair of 80mm f/12 refractors side by side on a Giro III mount.  The beauty of having two scopes of the same aperture and focal length on a side-by-side mount is that I can use different magnifications in each, and then jump between them to compare views.

And THAT means – this is going to be SMALL eyepiece night!  Both scopes will only hold a 1 1/4″ diagonal, so I’ll restrict myself to using Plössls and Orthos tonight – none of those large 1 1/4″ Radians, and definitely no monster two inch eyepieces!  So prepare to do some squinting into some small lenses.

From my observation site Cepheus is framed on either side by some trees, and oriented so that Gamma (γ) Cephei — the pointed end of the constellation — is pointing down, as shown in the map below.  That puts Omicron (ο) Cephei just to the left of a few tall firs.  In the bright moonlight, I can barely see it, but I’m able to line it up with a protruding tree limb very close to it.  So, resorting to a seldom used high tech approach, I center the tree limb in the 6×30 finder of the scope on the right and move to the left – and we have success!

Stellarium screen shot with labels added. Click on image for a larger view.

Omicron (ο) Cephei  (Σ 3001)           HIP: 115088    SAO: 20554
RA: 23h 18.6m   Dec: +68° 07′
Magnitudes: 5.0, 7.3
Separation:  3.35″
Position Angle: 222°  (WDS 2012)
Distance: 211 Light Years
Spectral Classification: G8
Status:  Physical, orbital chart can be seen here.

The Omicron pair is a tight 3.4″ apart.  I find that with a 20mm Plössl (60x), the secondary is just budding from the edge of the primary.  I drop a 15mm Plössl (80x) in the other scope and have a definite split, but replacing that eyepiece with an 11mm Plössl (109x) and then a 9mm Plössl (133x), I can see a respectable amount of black sky between the two stars.  I decide to try a 7mm Ortho (171x), but that dims the view just enough that the secondary becomes hard to see.  The best view is with the 9mm Plössl.  The primary is a very definite yellow in both scopes and in each of the eyepieces.  Observations in the Haas book include a yellow-green, which I don’t see at all.  That book also describes the secondary as blue, but in my scopes it’s too faint to determine a color – pale white is the best I can do.

Σ 2883  (H N 121)           HIP: 109474    SAO: 19922
RA: 22h 10.6m   Dec: +70° 08′
Magnitudes: 5.6, 8.6
Separation:  14.5″
Position Angle: 252°  (WDS 2007)
Distance: 106.5 Light Years
Spectral Classification: F2

Moving into the space between Beta (β) and Iota (ι) Cephei will get us near Σ 2883 (STF 2883).  Again, the moonlight is making it difficult to make visual contact, so I point the scopes to the  southwest of Beta (β) and then peer into one of those little 6×30 finders.  There is one advantage to the bright moonlit sky — I can clearly see the cross hairs in both finders.  I find what looks like the ideal candidate, center it, peer into the scope on the right which now has a 25mm Plössl (48x) in it because I need the larger field of view it offers — and we have contact!  These two are farther apart, but each component is a bit fainter.  The primary is a bright white, and the secondary is a just a pinpoint of faint light, clearly separated.  On a dark night, this would be a beautiful pair, but against the background of the bright sky, the 8.6 magnitude of the secondary is tending toward the weak side of faint.  The best view of this pair is with a 15mm Plössl (80x) — in the 11mm Plössl (109x), the secondary is difficult to see in the glare of the primary.  Moisture in the air seem to be doing it’s part to enhance the glare.

And, I see, there is quite a bit of dew collecting on the dew hoods of both scopes, and on the deck, and on the tops of my shoes!  Time to get up and take a short break — tea and cookies for me, a dog bone and water for Astro Klaus, my trusty side kick — stretch my legs, and dry things off  just a bit.

Image from Stellarium with labels added.

Σ 2923  (STF 2923)         HIP: 111325    SAO: 10418
RA: 22h 33.2m   Dec: +70° 22′
Magnitudes: 6.3, 9.2
Separation:  9.7″
Position Angle: 47°  (WDS 2007)
Distance: 400 Light Years
Spectral Classification: A0

Last, but not least, and not easy,  is Σ 2923 (STF 2923) — not easy because I can’t see it at all.  By now, Cepheus has rotated enough that Σ 2883 and Σ 2923 are just about horizontal, which should make navigation easy on the alt-az mount.  I can see by my chart that if I move to my right about 1.5 degrees, and then down slightly, I should pick up a distinctive group of three stars — the one degree field of view of the 25mm Plössl makes the distance easy to determine.  Finding the stars is not a problem, but visual confirmation of the double is another story.  It’s clear from the more detailed chart that the star in the middle of the configuration of three is Σ 2923, but it takes a good fifteen minutes and several repeated searches before I can confirm it.

small EYEPIECES! (Click image for larger view.)

My plan here was to start with the brightest of these three Cephean doubles and end up with the faintest, mainly because I needed the other two to help locate it.  So we’ve gone from magnitudes of 5.0 & 7.3, to 5.6 & 8.6, and now to 6.3 & 9.2 — a declining pattern of brightness that I hadn’t thought too much about when I started this.  But as the moon gets higher, the sky is becoming brighter, and the moisture in the atmosphere is following in step.  Leaving the 25mm in the scope on the right in case I need it for reference, I put a 20mm Plössl (60x) in the one on the left and finally am able to see the secondary, very faint and very close at 9.5″ from the white primary.  A 15mm Plössl (80x) brings it out well, but again, any more magnification than that just increases the glare and makes the secondary more difficult to see.

So, a damp night, damp clothes, dew-covered scopes, and all in all, a rather successful night.  I think I’ll come back again, though, when the sky is darker.  These stars are not at their best in this bright moonlight, and I suspect that Σ 2883, especially, will be a very rewarding sight in a 60mm scope.  Don’t wander off to far — I’ll be back!

The moon caught in the act of casting its reflected photons at a pair of 80mm f/15 refractors. The one on the left is a Sears model, with a Towa lens; the one on the right is an old Mizar, with a Carton lens installed in it.

Beautiful Xi Cephei guides you to a nearby 5-star multiple ΟΣ461

Xi ( ξ) Cephei (Kurhah)

RA: 22h 04m   Dec: +64° 38′
Mag: 4.4, 6.4   Sep: 7.9″   PA: 275°
Dist: 100 ly
Spectral Classification: A3

ΟΣ461 in Cepheus

RA: 22h 04m   Dec: +59° 49′

  • AB Mag: 6.7, 11.4   Sep: 11.1″   PA: 297°
  • AC Mag: 6.7, 10.0   Sep: 88.9″   PA: 41°
  • AD Mag: 6.7, 7.8   Sep: 184.7″   PA: 73°
  • AE Mag: 6.7, 11.4   Sep: 237″   PA: 38°

Note: Click  image at right to see all the data on this complex system from the Washington Double Star Catalog.

Five star isn’t a quality rating -it’s how many visible stars there are in this combo – or perhaps more if you apply enough  light grasp. But let’s start with Xi ( ξ).  It’s a piece of cake to find and yummy, too!

Haas rates it a “showcase” double and it deserves the title. Xi ( ξ) is an easy split – a 4.4 lemon yellow star and a 6.4 violet companion almost 8 seconds apart. While a 60mm should handle it, I found it very easy with the 76mm, even at 38X – and just plain pretty when I used a 13mm Plossl delivering 92X.  I found it with no trouble on the night of a full moon – in darker skies it would be even easier.  Cepheus forms a crude “home plate” with five bright stars, the faintest approaching magnitude 4. In the middle of the square part of this figure is Xi which at 4.4 I couldn’t see in the moonlight, but it stood out easily in the finder scope with no competing stars of similar brightness to confuse me.

Xi( ξ) serves as a guide to our second prize in the interior of Cepheus, the five-star multiple known as ΟΣ461. Now this was more challenging with plenty of nearby stars to confuse, but the beauty of it is this: It lies right on the same hour circle – almost to the second – as Xi ( ξ). So if you’ve found Xi, all you have to do is move due south  a bit less than 5 degrees. (Which way is south? It depends on the time of year and night – but simply find Polaris. Look at the direction to Polaris and move in the opposite direction. Your finder probably provides a  rough five degree fov to act as a guide as to how much.)

That’s the easy part. Now you need to be careful about the identification because I found at least one field that seemed to be the right one, but the star pattern I saw was simply too large. You need to be aware of what you are looking for – the chart below should help – and you need to be aware of the field of view of your eyepiece. (I was using one with close to  half a  degree field of view.)  This whole group of stars fits in about four minutes – so that meant it would take up a little more than one-eighth of the diameter of my eyepiece field.  Armed with that information, you can make short work of finding this. Without it, I spent quite a bit of time and frankly, part of what was confusing me was a little piece of text in the Haas book. But first take a look at this chart.

Click on image for larger version.

My problem is Haas says:

“The shape is pretty – three white stars in  a straight  line, all exactly alike, with a smaller star off to one side.”

When she says “exactly alike” I take it to mean roughly the same magnitude – and what jumped out at me were the stars I have labeled A, E, and X  seem to fit this description – but “X” is not part of the combination, it just fits her description. You could say she means A, C, and E – but E is so faint (mag 10) that I had to look hard for it under these conditions and  a 3 magnitude drop doesn’t fit the wording “exactly a like.”)

Bottom line – whether Haas confused “X” as part of  the multiple star or not, I think other observers might – I did, going on her description. It wasn’t until I started examining my notes and comparing them to Starry Nights Pro screen – which is where the image comes from, as well as the distances and PAs – that I noticed the problem.

In any event, ΟΣ461 is worth a second visit on a moonless night. This multiple is attractive – and once I got over the confusion, I liked including “X” in this equation – “X” makes for an especially pretty grouping whether it belongs to the gang or not 😉