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Way Up North in Cygnus: Σ 2687 (with Bu 433), Σ 2671, and HJ 1516

It took a few false starts, accompanied by a couple of enticing detours, but I’ve finally made it back to what I began three months ago.   As the rain comes clattering down outside in bucket after bucket, I find myself hovering over the sketches I did on that warm August night while Cygnus was winging its way over my head in slow motion.  Not only is distant starlight the equivalent of a time machine, but with their ability to remind me of the peaceful post-midnight quiet of that night, these sketches possess an element of time machine magic as well.

My telescope and I had journeyed to a remote northern outpost in Cygnus in an  attempt to find a reported Albireo imposter lurking in the vicinity of Σ 2687.   I searched diligently through the surrounding sky, but with no luck.  However, since I was climbing around rather aimlessly through this star-studded sector of the Milk Way, I thought it might be a good idea to familiarize myself with its double star population . . . . . . . which led me to a trio of multiple stars serendipitously and simultaneously visible within the five degree field of an 8×50 finder.

 The easiest way to get where we’re going is to find your way to 4.30 magnitude 33 Cygni.   As the chart shows, it’s located midway between 3.75 magnitude Iota (ι) Cygni and 3.43 magnitude Eta (η) Cephei.  I found it easiest to draw a line from 4.20 magnitude Theta (θ) Cephei to Eta (η) Cephei and then extend a line at right angles to that one a distance of six and a half degrees southwest to 33 Cygni.  (Stellarium screen image with labels added, click on the chart for a larger view).

The easiest way to get where we’re going is to find your way to 4.30 magnitude 33 Cygni. As the chart shows, it’s located midway between 3.75 magnitude Iota (ι) Cygni and 3.43 magnitude Eta (η) Cephei. I found it easiest to draw a line from 4.20 magnitude Theta (θ) Cephei to Eta (η) Cephei and then extend a line at right angles to that one a distance of six and a half degrees southwest to 33 Cygni. (Stellarium screen image with labels added, click on the chart for a larger view).

Here’s a closer look at that area:

Stellarium screen image, labels added, click to enlarge the chart.

Stellarium screen image, labels added, click to enlarge the chart.

 We’ll start by hopping one and three quarters degrees due east from 33 Cygni to the combined 6.55 magnitude light of Σ 2687, which forms a triangle with 6.10 magnitude HIP 101285 and 5.95 magnitude HIP 101084. (Stellarium screen image with additional labels, click for a larger view).

We’ll start by hopping one and three quarters degrees due east from 33 Cygni to the combined 6.55 magnitude light of Σ 2687, which forms a triangle with 6.10 magnitude HIP 101285 and 5.95 magnitude HIP 101084. (Stellarium screen image with additional labels, click for a larger view).

Σ 2687 (HN 89)  (S 753)           HIP: 100808   SAO: 32590
RA: 20h 26.4m   Dec: +56° 38’
Magnitudes: 6.37, 8.31
Separation:  26.9”
Position Angle: 118°  (WDS 2012)
Distance: 547 Light Years
Spectral Classification: B9, A2
Notes: “A” is a spectroscopic binary

There’s nothing like a good old fashioned, no-tricks, straight-forward double star to start a tour:

Against a background of very black sky studded with glittering points of diamond-like starlight, the primary struck me as pure white.  The secondary was several shades paler, verging on gray.    East & west are reversed to match the refractor view, click on the sketch for a much better version.

Against a background of very black sky studded with glittering points of diamond-like starlight, the primary struck me as pure white. The secondary was several shades paler, verging on gray. East & west are reversed to match the refractor view, click on the sketch for a much better version.

Click for a larger view.

Click for a larger view.

As the HN 89 catalog number in parentheses indicates, this is a William Herschel discovery.  He came across it on September 16th, 1792, describing it as “a little unequal” in reference to the magnitudes.  Although he didn’t provide measurements for it, Sir James South made up for it by measuring the pair twice in 1824, coming up with an average separation of 26.446” and a position angle of 119° 38’, not all that different from the WDS measurements of 2012.  His handiwork is visible at the right.

We’re looking directly into an arm of the Milky Way as we gaze into the eyepiece, so there’s no shortage of starlight for the roaming eye.  As my eyes leisurely wandered around the field of view on that night back in August, absorbing the numerous combinations and patterns of stars, they landed on a pair parked nineteen arcminutes south of Σ 2687 which turned out to be:

Bu 433         No HIP     SAO: 32592
RA: 20h 26.5m   Dec: +56° 19’
Magnitudes   AB: 8.95, 11.20     AC: 8.95, 9.90
Separations  AB: 8.0”                  AC: 29.20”
Position Angles   AB: 207°  (WDS 2011)    AC: 241° (WDS 2011)
Distance:  198 Light Years
Spectral Classification:  “A” is A2

S. W. Burnham discovered this pair in 1892 with his six inch refractor.  He measured it a second time in 1898, resulting in separations of 7.81” and 206 degrees for AB, 27.57” and 244 degrees for AC.  I wasn’t aware of “B” hiding in the weak glow of the primary at the time I first saw it, so it escaped my attention.  It should be visible in a six inch refractor, although I think averted vision would be a must.

Now let’s put 33 Cygni back in the center of the finder and locate Σ 2671.   You’ll find its sixth magnitude glow just forty arcminutes southeast, holding down the southeastern corner of a triangle it forms with 6.65 magnitude HIP 99955 and 6.55 magnitude HIP 99818.  (Here’s the previous chart once again).

Σ 2671 (H I 95)        HIP: 100097   SAO: 32455
RA: 20h 18.4m   Dec: 55° 24’
Identifier               Magnitudes      Separation      Position Angle        WDS
STF 2671   AB:    6.01,    7.51             3.80”                  337°                  2012
STF 2671   AC:    6.01, 12.40           87.20”                    53°                   2003
WOR 52      AE:    6.01, 13.70           30.30”                    54°                   2003
STF 2671   CD: 12.40,  13.30            5.20”                   137°                  2003
Distance: 291 Light Years
Spectral Classifications: “A” is A2, “B” is A0
Notes: AB is H I 95; “A” and “B” are spectroscopic binaries

This isn’t quite the complicated star it appears on first sight of the data . . . . .  mainly because some of the components refuse to come out of hiding:

 The first thing I noticed is the secondary is harder to see than its 7.51 magnitude would lead you to believe, but that’s mainly because at only 3.80” from the primary it suffers from that star’s white sixth magnitude glow.  In fact, the secondary had a tendency to fade in and out of view completely on the first night I looked at it due to poor seeing conditions.   (East & west reversed once more, click on the sketch to improve the view considerably).

The first thing I noticed is the secondary is harder to see than its 7.51 magnitude would lead you to believe, but that’s mainly because at only 3.80” from the primary it suffers from that star’s white sixth magnitude glow. In fact, the secondary had a tendency to fade in and out of view completely on the first night I looked at it due to poor seeing conditions. (East & west reversed once more, click on the sketch to improve the view considerably).

Once I had the secondary pinned down, I went in search of the other three components.  I found “C” easily enough, but after that I had to rely on averted vision to scoop stray photons out of the distant darkness.  There’s something very mysterious and ghostly about the small area in which the faint “C”, “D”, and “E” components are hiding.

I looked at Σ 2671 twice, once in August with a six inch Celestron f/8 refractor, and later on a cold end-of-October night with my six inch f/10 refractor as the temperature flirted with freezing.  Each time I strained my eyes unmercifully trying to pry “C” apart in hopes of getting a glimpse of its 13.30 magnitude “D” companion. I never succeeded, but I did manage to pull a 13.5 magnitude star out of that black island between “C” and the primary, which had possibilities of being the 13.70 magnitude “E” companion.   The problem was it didn’t match the 30.30” separation or the 54 degree position angle.

STScI photo with labels added, click to enlarge.

STScI photo with labels added, click to enlarge.

At the right you can see an enlarged photo of the tight area around Σ 2671 that I’ve rotated to match the sketch.  Sure enough, “D” and “E” are there, beyond the limits of my six inch scopes.

This is another William Herschel discovery which found its way into the eyepiece of his six inch reflector on September 22nd, 1783.  The “460” he mentions in his observation below refers to the magnification he used, and the “72° 15’ n. preceding” works out to a position angle of 342° 15’.

Herschel on STF 2671Based on his comment about “fine air”, he was enjoying some rather good seeing conditions on that autumn night in 1783, something I could certainly use a whole lot more of.   The Latin (according to my sophisticated Google translator) means “subsequent to the south”, which is a reference to Σ 2671’s position south of and following 33 Cygni, and it describes the location perfectly.

Now, on to our last star, which is barely over an arcminute southeast of Σ 2671.  You’ll find it at the southeast corner of a rectangle it forms with 7.50 magnitude HIP 100684, 7.45 magnitude HIP 100473, and 6.65 magnitude HIP 100526.  (Another view of our last chart can be found here).

HJ 1516  (h 1516)      HIP: 100744   SAO: 32566
RA: 20h 25.5m   Dec: +54° 41’
Magnitudes   AB: 7.25, 11.20     AC: 7.25, 11.80
Separations  AB: 46.90”             AC: 49.80”
Position Angles   AB: 147° (WDS 2003)   AC: 204° (WDS 2003)
Distance: 3000 Light Years
Spectral Classification: “A” is B2

 Even though the components are almost equal distances from the primary and are similar in magnitudes, the “C” component is conspicuously shy.   (East & west reversed once more, click on the sketch to enlarge it for a better view).

Even though the components are almost equal distances from the primary and are similar in magnitudes, the “C” component is conspicuously shy. (East & west reversed once more, click on the sketch to enlarge it for a better view).

Once again we have a white primary – there’s not a lot of color to be seen in this area – and a companion intent on playing hide and seek. The notes on my August sketch say “B” easy to see, “C” very difficult – fainter than listed?”  When I went back for another look at the end of October with my other six inch refractor I couldn’t see “C” at all, leading me to believe I had the wrong star.  I double-checked my location, didn’t see a problem, went back to the eyepiece for another look, and had a faint averted vision impression of a star where “C” was supposed to be.  It wasn’t until I increased the magnification that I was certain it was there.

Click on image to enlarge.

Click on image to enlarge.

Sir John Herschel, who discovered the AB pairing in 1828, apparently didn’t see “C” either, according to his observing logs that were published in the 1830-1831 volume of the Memoirs of the Royal Astronomical Society.  Considering “B” and “C” are at almost equal distances from the primary, it’s highly unlikely he would have excluded it if he had seen it.   The WDS shows a first observation date of 1912 for “C”, but I had no luck in finding out who made that observation.  My usual source, the bibliography available in Vizier, frustratingly skips over that date.

For a star that’s listed as only six tenths of a magnitude fainter than it’s very easy to see “B” sibling, plus being a mere three arcseconds further from the primary, “C” is a genuine enigma.   Either its published magnitude is too bright, or it could be the star is a deep shade of orange or red.   I discovered that Simbad assigns a visual magnitude of 11.9 to “C”, which is a move in the right direction, but not enough to explain its weak appearance.

So we’ll call HJ 1516 “C” contrary and difficult for now, wave good-bye, pick up our telescope, and head further south in Cygnus to see what other mysteries might be lurking around one of its stellar corners.  Be back soon!

Clear Skies!   😎

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