Now when you read the title of this post, your natural inclination would be to expect a star hopping tour through Aquila. But natural inclinations are like natural instincts — they’ll get you where you need to go in the vast majority of cases, but every now and then they’ll steer you down a perplexing path and leave you dangling at the edge of a perditious abyss. So, no —- this is not a four-starred star hopping expedition. Instead, this is a tale of how I happened to capture four multiple stars within the cramped confines of a 32mm Celestron Plössl in a five inch f/15 refractor.
Still, even though I’ve saved you from the potentially hair-raising horror of a bottomless abyss, I feel compelled to warn you: there may be moments in the adventure ahead where you’ll be inclined to pull a few hairs from your head. My advice is to wear a hat. Better yet, wear a helmet — and pull the chin strap tight.
How did I get myself into this torturous situation? Wasn’t easy, I must say, but it happened about like this:
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I was calmly poring over chart 66 of Sky and Telescope’s Pocket Sky Atlas while plotting a navigational approach to 56 and 57 Aquilae for the post prior to this one — when just to their southwest I spotted an alluring triangle of stars at the northeast edge of 37 Aquilae. One of the stars in that triangle even had the international symbol for a double star, that lovely horizontal line bisecting the center of it. My natural inclinations took control — which should have set off clanging bells of alarm, but didn’t — and I found myself overwhelmed by a ravenous exploratory desire.
I began to feed it by consulting Chart 19 of The Cambridge Double Star Atlas, hoping it would show more detail than the S&T chart —- it didn’t. Suddenly I felt the whirlpool-like pull of a frantic frenzy gaining control, so to keep it from forcing me into an extended internet research project, I flipped to page 20 of Haas’s book, and fortunately found this:
A low-power field, just northeast of 37 Aquilae, will show all three primary stars. 125mm: A hairsplit pair (Σ 2545), a slightly wider pair (Σ 2541), and a broad triplet that forms a straight line (Σ 2547).”
Three primary stars??? Three????? Praise printed material! My frantically ravenous frenzy was down to a mere rumble now.
However —– all of that was like a walk in the park in the twilight compared to what followed. Now I had to identify those “three primary stars.”
After some judicious searching in MegaStar and Sky Safari, I was able to apply the identities as shown at the right — and you’ll notice there’s an addition to the three Struvian delights, the mysteriously and cryptically named LV 21. I also discovered that when you include the non-duplicitous HIP 96479 with what were now four primary stars, they form an asterism remarkably similar to the Sagittarius teapot — heck, there’s even a spout arching off and up into the northwest! And if you study it a bit more, you’ll find an uncanny resemblance to the dreaded House of Hyades as well.
So after all that Struvian sleuthing, it was time to turn a telescope to the sky and see what I could see. And that’s when the twilight lit walk in the park came to a sudden crunching conclusion.
First, let’s step back and take a wide view in order to navigate our way to the target:
Now that we’re here, I’ll show you what I saw:
And when I looked in the eyepiece, I couldn’t make heads or tails, or doubles or triples, out of any of it. Now the field above was the one I finally settled on after roving around this area for the better part of an hour, so what is obvious in the sketch was not at all obvious in the telescope. Part of the problem was with the secondaries — they’re all faint, as in determinedly dim, and I didn’t see any of those I was looking for at first. Another reason was there were several strings of three or more stars scattered around the field of view — think back to Haas’s comment: “a broad triplet that forms a straight line (Σ 2547).”
Where in the pulsating blue light of a blazar was Σ 2547? Was it one of the three stars in the bottom right corner of the sketch?? Was it among the three at the top??? What were those three faint stars under the bright yellowish star at the top right center???? And what about the three stars at the bottom left????? So many questions and no known answers!
I peered into the eyepiece, then looked at a rough sketch of relative positions I had in my hand, looked in the eyepiece again, then back at the data I had in my other hand, went back to the eyepiece once more —- I panned up, I panned down, I panned sideways, I stood on my head —- I imposed position angles where they wouldn’t work, I tried separations that weren’t separated enough —– I muttered words I didn’t know I knew, I conjured up all kinds of contorted and imaginative pairings . . . . . . . . . . .
Argggggggghhh! Good thing I had a hat on my head.
So I broke a long standing ban on white light by going into the house, firing up the desktop computer that has MegaStar on it, and making a more detailed sketch of the area while blasting my night-adapted vision all to horrific Hades. But I was finally able to finally pin down the location of Σ 2547 — although it took several minutes for my vision to forgive me for that harsh treatment.
Σ 2547 HIP: 96646 SAO: 162847
RA: 19h 38.9m Dec: -10° 20′
Magnitudes AB: 8.1, 9.5 AC: 8.1, 11.1
Separation AB: 20.8″ AC: 49.8″
Position Angles AB: 331° (WDS 2007) AC: 142° (WDS 2000)
Distance: 362 Light Years
Spectral Classifications A: A0 B: F2 C: K1
It was in the bottom right corner! Its three stars were not quite in a straight line, either, I must say — which was a key contribution to my confusion — but nevertheless, they still formed an eye-pleasing faint arrangement of triple delight. (You can see full-sized versions of each of the sketches at the right by clicking on the image).
After achieving that hardly inconsiderable milestone, I had a point from which to navigate around the eyepiece. I found Σ 2545 next, in the top right center, but only after I looked very, very carefully and found it’s 8.5 magnitude secondary.
Σ 2545 (AB is H I 13) HIP: 96622 SAO: 162843
RA: 19h 38.7m Dec: -10° 09′
Magnitudes AB: 6.8, 8.5 AC: 6.8, 11.6
Separation AB: 4.0″ AC: 25.4″
Position Angles AB: 326° (WDS 2008) AC: 163° (WDS 2000)
Distance: 263 Light Years
Spectral Classification: A9
After spying its dim light hiding behind the slight yellow-gold glow of the primary, it was as obvious as the moon at midnight. Even so, the 11.6 magnitude “C” companion was easier to see, and it was one of a line of three faint stars that had confused me from the beginning.
And that led me up to LV 21, which I pinned down only after I confirmed the identity of the very faint and barely separated BC pair in my telescopic microscope.
LV 21 HIP: None listed SAO: 162829
RA: 19h 37.7m Dec: -09° 58′
Magnitudes AB: 7.2, 10.2 BC: 10.2, 11.3
Separation AB: 86.5″ BC: 4.1″
Position Angles AB: 285° (WDS 2010) BC: 285° (WDS 2002)
Spectral Classification: A2
That BC pairing was a prime suspect from the start — all I needed was enough magnification (100x) in the five inch f/15 to pull them definitively apart, after which I could detect both stars easily enough at the 60x used for the first sketch above. Again, it was part of a line of stars that had me roundly confused — there were four of them, and I had tried to break them down into either a group of three on the left or three on the right. As it turned out, the star on the east edge of that string is an impostor hoping to convince an innocent visitor like me that it’s a member of the system.
So what happened to Σ 2541??? According to Haas, it was slightly wider than Σ 2545, which she described as “hairsplit.”
Well sure, Σ 2541 is slightly wider than Σ 2545, but the primary is also two magnitudes fainter to begin with, and its secondary is 1.5 magnitudes fainter than that of Σ 2545. Add in the fact that both stars have a slight reddish-orange tint, which matches up well with their spectral classifications, and they’re even a bit fainter than if they were Class A stars like all of the others here. All of which means Σ 2541 has elevated elusiveness to a Burnhamian level of difficulty — in fact, even in the six inch f/8 refractor I used for the sketch shown a few lines above, I had to look very, very closely to see the secondary. I had looked right at this star several times on the first night I observed it and never once saw the first glimmer of secondarial light escaping from it. But 100x did the trick again that first night — and again, once I had picked it out at that magnification, I could see it at 60x in the five inch f/15, but only if I was very precise with the focus.
So let’s look at that first sketch above again, and this time with labels:
Now obviously this is not a task to be tackled with a small aperture scope — at least not if you want to pry into the tight spaces which are typical here. Five inches is probably the minimum of what will work (an optically perfect 100mm scope might work), six inches undoubtedly is a better choice, and anything over that should provide an outstanding view if you can keep all five stars in the same field. The night I made all of the individual sketches shown above along the right edge of the data listings, I used my six inch Celestron f/8 — and due to persistent haze, I really didn’t do much better than I did on the earlier night with the five inch f/15 D&G.
One other thing before winding this sagacious saga up — actually another question, as if there haven’t been enough already: What in the world does the LV in LV 21 stand for?
It stands for Leavenworth, as in Francis Preserved Leavenworth, who was director of the University of Minnesota Observatory for thirty-five years. He published a book in 1930, Measures of Double Stars, and a review of it is available here. I’ve searched the internet for that book and haven’t been able to find it, but it can be found in numerous libraries around the world — you can locate the closest one to you by going to World Cat at this address. And one final touch: a photo of F.P. Leavenworth
Let it never be said that I would leave a stone unturned somewhere. 😎
Next time out, we’ll move into northwest Aquila for a look at two very different stars —- but first, I need some CLEAR SKIES!!!!!! And soon!