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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.   😎


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