September 20th, 1783, about 4 AM
It had been clear and comfortably cool most of the night, with a few thin clouds slipping past occasionally, but now the temperature was beginning to drop and the dampness was coming up as the morning dew formed across the grass covered landscape. Silence ruled everywhere, except behind the garden, where the creaking and groaning of the twenty foot long Herschel telescope punctured the calm air at random moments.
Wrapped in a long wool coat to ward off the dampness, William Herschel was perched comfortably at the eyepiece, while his sister, Caroline, sat in a small enclosure below the telescope. From time to time, he would call down right ascension and declination coordinates, and she would record the information while referring to a copy of Flamsteed’s Atlas Coelestis which she kept open on a desk in front of her.
With no warning, he suddenly leaped from his chair and called down to his sister to come upstairs immediately. Accustomed to his sudden and unpredictable outbursts of enthusiasm, Caroline climbed the stairs slowly, and following his frantic gestures, walked over to the eyepiece, bent down to take a look and hovered there for about twenty seconds, then looked up at Sir William with a quizzical expression on her face, bent down and looked again, only longer, and then, quite suddenly, exclaimed: “Well shivering secondaries, Will! If that isn’t the most beautiful thing I’ve ever seen, I’ll sell all my Naglers!”
And that, fellow Star Splitting enthusiasts, was the morning Sir William discovered the gem we’re about to dissect in detail. 😉
(Tip: In the link above to the Atlas Coelestis site, scroll a bit more than half-way down in the box at the left to see Flamsteed’s chart of the Orion-Eridanus-Lepus area).
H III 111 (Σ 758) (AE also identified as S 493)
HIP: 26494 SAO: 132385
NOTE: AB is Σ 757; AC, AD, and CD are Σ 758
RA: 05h 38.1m Dec -00° 11′
***** Magnitudes Separation Position Angle WDS Data
AB: 8.0, 8.3 1.5″ 240° 2008
AC: 8.0, 8.7 51.4″ 87° 2003
AD: 8.0, 8.5 41.5″ 79° 2002
AE: 8.0, 8.7 138.3″ 263° 2003
CD: 8.7, 8.5 11.2″ 298° 2006
Distance: 741 Light Years
Spectral Classification: All B6
I’ve been curious about this multiple star since I first came across a reference to it in Sir William’s Double Star Catalog. His description there includes precise, if cryptic, directions on how to get to it:
Treble. About 1-1/4 degree n. following epsilon, toward alpha Orionis. The two nearest of the third class.”
The “third class” is a reference to his cataloging system, which was based on the separation between stars. In this case, the Roman numeral “III”, which designated separations of five to fifteen arcseconds, was used to describe the CD pair.
Which also pretty well explains the origin of the unusual designation, H III 111, of this multiple system. You’ll actually find it on most charts as Σ 758 (Struve 758), but somehow that label lacks the uniqueness conveyed by H III 111. And unique this multiple star certainly is.
Since Sir William’s directions are still good 228 ½ years later, we’ll just follow along to get where we need to go.
The “epsilon” mentioned above in Herschel’s catalog description is Epsilon (ε) Orionis, also known as Alnilam, which is the center of Orion’s three belt stars. His description, “following epsilon,” means our target is east of Epsilon (ε), which you can confirm (once we have it located) by looking into your eyepiece (with the drive turned off!) and watching H III 111 follow Alnilam’s apparent motion across the field of view. But he also said something about 1 1/4 degrees north, so let’s position Alnilam at the west edge of our field of view, and then nudge our telescope very slowly north (it won’t take much!) — and if you watch the northeast edge of the field, you’ll see this image come into view at low magnification:
The pair of close stars your eyes are attracted to first are AB and CD (they’re labeled in the sketch below). “B” is almost glued to “A”, at a mere 1.5 arcseconds of distance, and requires at least five inches of aperture in average seeing conditions to be seen. On the other hand, 8.5 magnitude “D” is much more friendly to prying eyes at a distance of 11.2 arcseconds from “C”. And drifting to the west at just beyond a full two arcminutes of distance, and leading the whole complicated complex through the sky, is 8.7 magnitude “E”, which is easily seen in either the sketch above or below, just to the left of AB. There’s another star on the east side, almost in a direct line with all of the others, which looks like it could be part of this system. It isn’t — but it does serve to balance out the visual view of this group of stars.
Now the thing I really like about this quintuple grouping of stars is — as the title states — that there’s something here for any aperture. On that first sight of H III 111 in a 50mm or 60mm scope, your eyes gravitate to three stars: AB, CD, and E. All three of them are relatively dim, and if it weren’t for the fact that they’re almost in a straight line, your eyes would pass right past them in search of more stimulating visual material.
But, if you care to be persistent, you can pry “C” and “D” apart with either of the small apertures. I did it in my 50mm Zeiss f/10.8 with an 11mm TV Plössl (49x) and a 7.5mm Celestron Plössl (72x). In the 11mm eyepiece, the two stars could be seen clinging tightly to each other, with maybe a hair’s width between them, while the 7.5mm Plössl produced a definite separating slice of dark sky in the intervening stellar gap. Although that view would never win any awards for radiant brilliance, it was just tantalizing enough that I was reluctant to move over to the 60mm scope.
However, I eventually did — and as you would expect, the view in the 60mm scope was about ten millimeters better. Seriously, confined as we are here between the upper and lower ends of the eighth magnitude bracket, that ten millimeter difference was noticeable. In my f/13.3 version of the sixty millimeter refractor, the 11mm TV Plössl (73x) view was pretty much the equal of what the 7.5mm Celestron had been in the 50mm scope, although just a bit brighter. When I put the 7.5mm eyepiece (107x) to work in the 60mm scope I was back to dim, but it was still a stunning view — when it stopped bouncing around like a mad hornet confined in a jar. The seeing on that particular night was poor, somewhere between a I and a II (on this scale), but at unpredictable intervals, it would suddenly improve for as much as a couple of minutes.
But — a few nights later, with seeing equal to about a IV, I was caught completely by surprise when I took another look at the CD pair in the 60mm scope. With the 20mm TV Plössl (40x) placed provisionally in the diagonal for locating purposes, both of those stars were separated just as clearly and cleanly as if I was using twice the aperture — something I really hadn’t expected to see. I suppose Mother nature was providing me with a tantalizing reminder of how much easier stable seeing can make things — which really would have come in handy later on, as you’ll soon see.
Now the view of the CD pair improves by several hundred percent when you increase the aperture to 90mm or more. I’ve viewed H III 111 in an inexpensive 90mm Orion refractor, a more expensive 100m refractor, and an f/15 127mm refractor at low magnification, and in each case, the CD pair greets you immediately and separately at low magnification, as in the sketch at the right. No fuss, no strain — you would never guess the two of them appear as one star in smaller apertures.
But to reveal the duplicity lying deep within the AB pair, you’re going to find you need at least five inches (127mm) of aperture, steady seeing, and an absence of atmospheric muck, which is something that clogs the local coastal air at this time of the year. Most people would call it moisture, but I prefer muck because it’s like looking through a thin layer of mud.
Bright stars, such as Alnilam, look like they’re surrounded by a glowing cloud of nebulosity that’s busy chewing away at the smooth round edges of the star, and faint stars become dim or disappear into it entirely — kind of like quicksand. I wouldn’t even bring it up, except that every time I tried to pull the AB pair apart in a five or six inch scope, all I got was elongated streaks — and after several attempts under those conditions, my patience was reaching an elongated stage as well.
But it’s at the larger apertures that this quintuple system really comes alive, so one way or another, I intended to see it for myself, even if it took until April. Remember, Sir William and Caroline were looking at it through a 20 foot long reflector with a 12 inch mirror, so despite the fictional reaction I portrayed above with a modest amount of imagination, their view must have been spectacular. I can’t approach anything of that sort, but I knew I could improve considerably over the 60mm view.
So I waited ………. and waited ………… and waited some more ……………. and then some more ………….. heck, the rain and clouds were so thick during all that waiting that my eyes almost became permanently dark adapted.
But finally, on February 27th of the current year — in case you’re keeping track, that would be 228 years and five months after Sir William discovered this gem — I managed to coax an hour of clear skies out of the Sky Gods, the last half of which was invaded by the wet, high altitude muck I’ve described above.
I was using the five inch f/15 D&G refractor shown above, which miraculously landed in my hands several weeks earlier, and was sure I could crack the AB pair with it even though I hadn’t had any luck in its earlier attempts in the celestial muck. But this time, I intended to sit there through the next cycle of rain-hail-snow-sleet-wind — or whatever else the Sky Gods threw my way — until I got it.
I started with a 30mm Take LE (64x) for the relatively wide view and found “C” and “D” dancing separately, but in unison, so I began an upward migration into the ethereal realm of higher magnification. The D &G has a focal length of 1905mm, which almost matches the focal length of an eight inch f/10 SCT (2000mm) — meaning the “X” factor increases quickly if you’re not paying close attention to it.
With noticeably more light gathering ability than a four inch refractor, I thought I might meet with a successful glimpse or two in a 20mm TV Plössl (95x), but no such luck — the moisture-laden muck had already begun to invade. I had what might have been a glimpse of the pair with my next move up, a 15mm TV Plössl (127x), but the image had now decided it was time to jump up and down and sideways. Instinct whispered to me about that time, telling me to make a desperate lunge into the land of Barlow — either do what it took to get it now, or risk sitting here for the next week or more, dripping in the wind and rain, waiting on a suitable sucker hole.
With my back wedged against the metaphorical wall, I reached into my coat pocket, extracted a plastic bolt case, removed the top, and pulled out the secret weapon — a 2.4x Dakin Barlow, which alters the “X” factor in long magnified leaps. Back to the 30mm Tak LE, which magically became a 12.5mm eyepiece (152x) when I slipped it into the Barlow — but no luck. I tried a 24mm Brandon next, which was transformed into a 10mm Brandon (191x) — maybe, not quite sure really, lots of hopping going on. Then, on to the 20mm TV Plössl, now in it’s 8.3mm incarnation (230x), and the hopping was almost hopeless. And the image was disappointingly dim.
Even with a five inch refractor, magnifying two almost glued-together eighth magnitude stars two hundred and thirty times tends to filter out a lot of photons. And when the image is jumping very energetically all over the field of view, the few photons that find their way to your eye don’t stay there for very long — micro-seconds at the most. But I kept staring, and the image kept hopping, and the atmospheric muck kept increasing, which kept dimming the image even further — but I kept staring anyway.
Back when I started with the 30mm Tak at 64x, “C” and “D” were two well-rounded orbs of light. But now, mired in the muck at 230x, they were two oblate, moth-eaten smudges of something or other that you would never mistake for points of light. I knew deep in the depths of my starlight starved soul that I was walking the equivalent of an optical plank, and I was within a few steps of the end of it now.
And then I caught a glimpse of two distinct points of light where AB was. Not for long — in fact, if I had blinked right at that moment, I probably would have missed them altogether. I eased back from the end of the plank and looked again.
Yes! There they were! ………………….
And there they went ……………………………………
But they came back several times, and a few of those times, I got a very distinct view of two very separate, almost round dots of very small light. It was strange — I had expected to see two stars about the same diameter as “C” and “D”, but instead they were about half of that.
Well, heck, what happens if I promote the 15mm TV Plössl to a 6.25mm version with the Barlow? 305x, that’s what, and mostly mush.
I edged carefully away from the optical abyss beyond the end of the plank, went back to the 230x view, and managed a few more glimpses of “A” and “B”, separated by about a photon’s worth of width — and then they morphed into mush, too.
So I retraced my steps in reverse — 191x, 152x,127x, 95x, and finally to 64x — and as fast as I moved in reverse, the incoming muck moved even faster. The view didn’t improve one smidgen of an iota as the magnification dropped and the field expanded.
I looked up at the sky for the first time since I had started with the Barlow — and the only thing I could see was a smeared image of a crescent moon over in the southwest, swimming in a sea of haze and elongated gray clouds.
Well …………. geez ………………….. what a revelation that was.
But I had what I came for, and if it was hardly a satisfying image, it was still a very tantalizing hint of what would be possible under better conditions. And this being the north coast of Oregon in February, I was really darn lucky I had captured it.
But I do plan on returning with a six inch refractor, and probably an eight inch SCT, too, when the skies eventually re-open for business. I would love to get at least 1/24 of a taste of what Caroline saw (“Well shivering secondaries, Will! If that isn’t the most beautiful thing I’ve ever seen, I’ll sell all my Naglers!”) in Sir William’s f/20 twelve inch mirror that night.
Clear Skies! ——- And if you have more than you need, send the surplus in this direction. 😎