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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!

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2 Responses

  1. Hi Star splitters this has got to be the best site for double star info i have come across,have been on a few but this is the best,it has been an education looking through the star charts and diagrams plus the photos of the the different telescopes .I have two zeiss scopes the 63/840 telementor and the 63/840 telemator, i think they are the holy grail for double star observation ,but i can see as i look through this site there are many scopes up to the job ,anyway dark skys to all

    • Thanks for the kind words – and yes, those Zeiss scopes have a super reputation and I know John has one, but I’ve never looked through one. I remain happy with my 60mm Unitron and 50mm Tasco, though when I was a kid I would never dream of mentioning the Tasco in the same sentence as the Unitron – let alone the Zeiss 😉

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