So there we were, me and my 80mm Mizar, sitting quietly in the moonlight. The sky was magnificently crisp, the stars were twinkling with adolescent enthusiasm, a rapturous host of beautiful fluffy white clouds were arrayed randomly above me — and I was mentally preparing myself for an invigorating evening of sucker hole roulette. You probably know the routine: find the most wide open space of sky you can (get ready to spin the roulette wheel), aim your scope at a target in the middle of it (spin the wheel now), get lined up (it’s slowing down already), focus the image (it’s really slowing down now), and then guess how long it will be before the clouds invade your field of view (the wheel is barely moving at all now). Usually it takes no more than a fraction of a second after you find the focus (yep, just heard the marble drop). Fun stuff if you have the patience for being fleeced repeatedly. (It doesn’t matter where the marble drops, you won’t win).
But as the evening wore on, the clouds became less common and the sucker holes began to get larger and more long-lasting. So I stuck with it, zeroing in on a target and staying with it for as long as I could see it. At some point – I think it was about the time my fingers had turned to ice and my toes were as hard as permafrost – I spied a huge swath of clear sky in Canis Major. And that was when I remembered the Winter Albireo, thanks to a recent email and sketch from Steve McGee.
So I grabbed my well-worn copy of Sky and Telescope’s Pocket Sky Atlas, flipped to chart number 27, and star-hopped around the coastal pines to it.
I didn’t mention the coastal pines? They’re a family of inter-woven and close-knit fir trees living across the street from my second story deck — there are about a dozen of them — that project eighty feet into the air, blocking most of my view of the southern sky below a declination of minus ten degrees or so. I keep waiting for a winter wind to take them down, but no luck so far. Anyway, since the Winter Albireo lies at a declination of minus twenty-three degrees, that meant I had replaced the art of sucker-hole-hopping with a challenging game of fir-tree-finesse. So with mother earth escorting them through the lace-like framework of pine needle branches, I spent the next hour catching views of three of John Herschel’s 1837 discoveries.
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It was November 13th, 1833 when Sir John, with firm intentions of completing a survey of the southern skies, packed up his astronomical hardware (including a five inch refractor and an 18.25” reflector) and boarded the East India Company’s Mount Stewart Elphinstone, bound for The Cape of Good Hope. During his sojourn there, he made a large number of double star observations, which are preserved for posterity on pages 171 to 242 of the book that resulted from that trip, Results of Astronomical Observations Made During the Years 1834, 5, 6, 7, 8 at the Cape of Good Hope; Being the Completion of a Telescopic Survey of the Whole Surface of the Visible Heavens, Commenced in 1825. That long-titled book, which was published in London in 1847, has fortunately found its way into the public domain and can be found here.
And we’re here to take a look at three of those stars now, beginning with h 3945, sometimes referred to as the Winter Albireo.
h 3945 (BC is SHY 508) HIP: 35210 SAO: 173349
RA: 07h 16.6m Dec: – 23° 19’
Magnitudes AB: 5.00, 5.84 BC: 5.84, 6.76
Separations AB:26.40” BC: 999.90”
Position Angle: 52° (WDS 2008) 165° (WDS 1999)
Distance: 6273 Light Years
Spectral Classification: K4, A5
Before we get too far, I should mention you’ll find the stars catalogued by John Herschel carry a prefix of “HJ” in the Washington Double Star Catalog (WDS). But the older lower case “h” is still used on many charts, so there’s no telling which style you’ll run across. I prefer the historical aura of the lower case format, which was originally used to differentiate the younger Herschel (h), Sir John, from the senior Herschel (H), Sir William, an effective visual form of paternal recognition if ever there was one.
I first bumped into h 3945 by accident several years ago when I was exploring the star fields east of Canis Major for open clusters. I think I had wandered north to it after ogling NGC 2362, a tight little cluster of stunning beauty surrounding Tau (τ) Canis Majoris which just happens to include another John Herschel discovery, h 3948. That one is a complex quadruple star that also includes two additional sub-arc second companions, and with a bit of cooperation from the winter skies, it may be the subject of a another post.
But for now, let’s go see why h 3945 picked up the Winter Albireo designation:
I don’t have the least clue as to who was first to describe h 3945 as the Winter Albireo, but as the colors in Steve’s sketch show, it was inevitable. Haas describes it as “bright citrus orange” and “royal blue” (p. 38), and the Night Sky Observers’ Guide describes it as “intense orange and blue” (Vol 1, p. 88). In his 1894 Celestial Objects for Common Telescopes, the Reverend T. W. Webb was considerably more impressed: “fiery red, greenish blue . . . Magnificent pair.” (64) And even John Herschel, normally rather reticent with descriptive notes, recorded the colors he saw in two separate observations, as can be seen at the bottom of the page at the right:
Not only is h 3945 deserving of comparison to Albireo, it also measures up well with Almach — but despite that, it does disappoint on occasion. I think it’s mainly a northern hemisphere thing, a result of the colorful pair’s relatively low position in the southern sky, which tends to diffuse the colors considerably when haze is present.
On the night I tracked it down with my 80mm Mizar, the sky was crisp and transparent, but the moon, waxing at about 60% of full, was bright enough to turn the orange tinge very pale, and the blue was barely detectable. So if you’re not impressed, go back on a better night – and to give the color a chance to work its magic, go with four inches of aperture or more if you can. My first view of it was in a four inch refractor, and that initial image still flickers to life every now and then in my double-starred memory.
There’s supposed to be a 6.76 magnitude third component, SHY 508, which is shown in the data line above with a position angle of 165 degrees at a distance of 999.90” (16.7’). The problem is it’s not there — not in Steve’s sketch, not in my copy of MegaStar, and not in the STScI photo at the left.
As you can see, I’ve labeled two possible candidates in the STScI photo. The fainter of the two, GSC 6537:2093, is at the correct PA and distance, but at a magnitude of 10.8, it’s too dim. The only star in the immediate area that comes close to matching the magnitude recorded for SHY 508 is 6.30 magnitude HIP 35132 / SAO 173319 / HD 56341, but at a PA of about 200 degrees and a distance of slightly less than 30 arc minutes, it’s in the wrong place. So – another mystery for the books. Or perhaps it’s just “SHY.”
Time to remove the mystery hat and clamber off to the north now, and to aid our navigation we’ll employ another chart:
h 3938 HIP: 34940 SAO: 173247
RA: 07h 13.8m Dec: – 22° 54’
Magnitudes: 6.32, 9.10
Position Angle: 250° (WDS 1999)
Distance: 1576 Light Years
Spectral Classification: B2, G5
Besides playing hide-and-seek with the interfering framework of pine needles, I was also contending with rather poor seeing once again, easily as bad as the worst shown on this chart. And there were other factors of frustration as well. The first was the 2.8 magnitude difference between the two stars, the second was the sunlight reflecting recklessly from 60% of the moon’s surface, and the third was the challenge the 9.1 magnitudes of secondarial light posed to an 80mm lens operating at 60x — more magnification just led to a muddled view. So despite the reasonably wide separation of 19.4”, I had to look long and hard to corner my quarry — it was averted vision or no vision. Fortunately, it didn’t take all that much visual averting to see the secondary, but it was very ghost-like at first. It easily could have been a creation of my imagination on first sighting, so I kept coming back to it as I made my sketch:
I really think this pair of stars is crying out for more aperture. It was certainly a challenge with the 80mm scope — an additional twenty millimeters would be a much better choice. Both stars were essentially colorless under the observing conditions I was contending with, but if you look up in the NNW corner of the sketch, you’ll see a sixth magnitude star that has a very pronounced orange tint to it – that’s HIP 34914, a class K4 star at a distance of 780 light years, which we saw earlier in our finder.
h 3934 (BC is RST 4840) HIP: 34718 SAO: 173152
RA: 07h 13.3m Dec: – 21° 48’
Magnitudes A,BC: 6.91, 8.49 BC: 8.60, 10.80
Separations A,BC: 13.7” BC: 0.60”
Position Angles A,BC: 235° (WDS 1999) BC: 270° (WDS 1949)
Spectral Classification: B5, B9
Now, with our previous pair still centered in your finder, if you use HIP 34914 as a pointer (here’s the chart above), you’ll find h 3934 shining as a 6.9 magnitude star at three times the distance separating h 3938 and HIP 34914.
And again, I had to avert my vision to catch a glimpse of the 8.49 magnitude secondary (we’ll skip “C” since it’s well out of reach for 99.99% of us):
The magnitude difference is only 1.58 between this primary-secondary pair, but they’re six arc seconds closer than our previous Herschel duo, which pretty much gobbles up what would otherwise be an advantage. In fact, the secondary here was every bit as eager to avoid my vision as that of h 3938. Again, I heard a voice echoing in the moonlight – more aperture! And sure enough, when I went looking for other observations of these two Herschel discoveries, I found Haas had come to the same conclusion:
h 3934: “150mm, 36x: Nice view. A bright, easy pair at the end of a curved line of dim stars. It’s a pure white star and an ash white, split by only a small gap.”
And our previous star —
h 3938: “125mm, 50x: Lovely combination. A bright white star with a small nebulous companion, split just wide enough for the companion to be easily seen while striking in contrast.” (p. 38 for both)
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And that was about enough for me on this particular night. Apparently intermission was over since the clouds were drifting back into their places in the sky in groups, the wind was winding itself up for another blustery show, and a persistent image of steaming hot tea was dancing in my head.
With any luck at all, next time out we’ll see if we can dig h 3948 out that open cluster surrounding Tau Canis Majoris.