I’ve lost count of the number of times my eyes have been drawn to the northeast corner of Corvus in the past few years, lured there by the attraction of Algorab and Eta (η) Corvi, which form a visual double you just can’t miss.
Crows have a reputation for being attracted to bright, gem-like objects, and then hiding them in a secret location. This Corvian crow is no exception — it’s managed to squirrel away a very attractive double and two tantalizing triples, all within a few degrees of it’s signature double, Algorab.
And the best part is that you don’t have to search very hard to find them.
Although it did take about three weeks in this case. Due to another long streak of uncooperative weather, I found myself cawght — for you non-Corvians out there, that would be “caught” — in northern Corvus trying to catch that ideal combination: a clear night with minimal haze along the southern horizon, and a sky dark enough to see some of the fainter components of the two triples. I didn’t think that was asking for too much from the Sky Gods, but they apparently felt otherwise — and I’m running out of eyepieces to sacrifice to those guys.
Corvus has a rich history of lore associated with crows and ravens. The German name is Der Rabe, which has something of a mystical quality associated with it — as in Hermann Hesse’s novel Demian, where the raven becomes the egg cracking Der Sperber in search of a new world. It’s one of the smaller constellations, but between its variety of double stars and a much-photographed deep sky object — the famous interacting galaxies known as The Antennae — it deserves more attention than it gets. And in the northern hemisphere it certainly doesn’t get a lot help from it’s low position in the southern sky.
We’ll start this Star-Splitting tour with the brightest of the bunch, Algorab, but be prepared to strap yourself into your chair — we’re going to spend most of our time out on the curve of Corvus’ wings. I don’t want anyone sliding off and out of sight beyond the horizon when those wings start flapping. 😉
Algorab (Delta (δ) Corvi) (Sh 145) HIP: 60965 SAO: 157323
RA: 12h 29.9m Dec: -16° 31′
Magnitudes: 2.95, 8.47
Position Angle: 213° (WDS 2012)
Distance: 88 Light Years
Spectral Class: A0 and K0
From my second story observing deck Corvus barely hovers above a cluster of tall coastal pines, putting it right in the midst of the haze drifting in from the ocean which is typical for spring on the northwest coast of Oregon. The first evening I tore myself away from the current close encounter of Saturn and Porrima to take a look at Algorab, the haze was so thick and the seeing so poor that I couldn’t even get a sharp focus on it. But I never give up — just like a recurring dream, I was back the next night.
And under much better conditions. I was using my Meade AR-5 (127mm), which treated me to a splendid sight in an 18mm Radian (66x) — it more than matched Hass’s description of Algorab as a showcase pair. In a 60m scope at 25x, she saw “A beautiful straw-yellow star that is brilliantly bright with a sharp little gray dot beside it — it looks like a star with a planet!” Admiral William Smyth saw it as “pale yellow and purple” — purple? I saw a slight bit of yellow in the primary and would lean toward describing the secondary as “whitish,” creeping toward gray. As low as it is in the sky for me, though, I suspect Haas’s description is a better choice. No cawmment on the purple.
I had a 20mm TV Plössl (45x) in the 60mm f13.3 Lafayette refractor which is mounted on the Meade scope, and found it was a bit of a struggle to pry the 8.5 magnitude secondary out of the primary’s glare, mainly because the horizon-hugging haze was smothering some of the photons before they could reach the 60mm lens. I could do it with averted vision, but direct vision only produced an occasional glimpse of it. From my location the transparency in the local southern sky is generally poor until autumn — and Corvus will have flown well out of sight by that time.
The name Algorab can be traced back to the Arabian name for raven, Al-ghoráb, which Admiral Smyth noted in his Bedford Catalogue of 1844. One of the most remarkable things about these two stars is how young they are — Kaler estimates them as only 110 million years old …… which on an astronomical time scale means they were born just a few days before yesterday. The secondary shows evidence of being surrounded by a disk of dust — not surprising considering its young age — which could condense into planets sometime in the distant future.
(HIP: 59426 SAO: 157133)
RA: 12h 11.4m
Dec: – 16° 47′
Magnitudes: 7.17, 8.79
Position Angle: 300° (WDS 2010)
Distance: 83 Light Years (Simbad)
Spectral Class: G6 and G7
Moving over to the opposite side of the Corvian rectangle, you’ll find Gamma (γ) Corvi, also known as Gienah, which appropriately enough means the right wing of the raven, as noted here by Allen (about two-thirds of the way down the page). It forms a triangle with sixth magnitude HIP 59895 to the north, and with our next star, S 634 to the northwest.
After spending quite a bit of time on Algorab, I had to look twice to see both of these stars. Using the 18mm Radian (66x), I would describe the split as very delicate — as well as a beautiful sight. It cried out for more magnification, though, so I jumped up to 118x using a 10mm Radian. S 634 is located in a fairly sparse field — at least in the haze — so it stands out quickly from the background stars at the higher magnification. Because of the haze and an invasion of poor seeing, I didn’t try the 60mm scope on this pair. Haas describes them as “an exactly equal mix of yellow and orange” — but all I saw in that haze was a maze of grays.
And now that we’ve warmed up on Algorab and this delicate pair, we’ll head over to Corvus’ eastern wing and begin the real show ………..
Σ 1669 (STF 1669) HIP: 61910 SAO: 157448
RA: 12h 41.3m Dec: -13° 01′
Magnitudes AB: 5.88, 5.89 AC: 5.88, 10.30
Separation AB: 5.20″ AC: 59.50″
Position Angle AB: 314° (WDS 2013) AC: 229° (WDS 2000)
Distance: 257 Light Years (Simbad)
Spectral Class: “A” and “B” are F5
As I’m typing this, my eye catches the word “spectral” on the data line just above, which prompts another word from my Star Splitter memory — spectacular — which this pair certainly is. These two stars are remarkably similar to Porrima. While not as bright, they share the characteristic of both components having the same magnitude. They’re farther apart — 5.3″ vs. the current 1.7″ for Porrima (Spring, 2011) — which makes them a good preview of what Porrima will look like in a few years as its “A” and “B” components get farther apart.
Again, like Porrima — the comparison is unavoidable — they’re both the same color. I saw a tinge of white in both of them, but really I would describe them as more yellow than white. Webb seems to agree with me: “yellow-white” — but Haas is at her best with her description: “Grand sight! A close pair of bright twins, peach white in color, that completely dominate their field.”
And that’s one thing about these two stars that you notice immediately — they really leap out at you from a black sky because they’re in a very sparse field of stars. In fact, I had to duck when I saw them coming at me because they looked like a pair of headlights.
Haas’s observation was in a 60mm scope at 35x. My 60mm f13.3 at 42x found them to be a bit difficult to split, but that’s because the smaller aperture just couldn’t penetrate the haze that night. I was back a week later, though, and under darker skies and improved transparency, they both were easily split in a 60mm f15 at 45x. On that night they certainly earned Haas’s “grand sight” description — two very small, barely separated, white points of light gleaming against a velvet background of black sky. It was worth waiting another week to catch them like that in a 60mm scope.
And now we’ll work our way a bit farther to the west and feast on a a couple of Triple Delights ……………….
Σ1659 (STF 1659) HIP: 61466 SAO: 157384
RA: 12h 35.7m Dec: -12° 01
Magnitudes A: 7.94 B: 8.34 C: 10.89
Separation AB: 27.5″ AC: 42.6″
Position Angle AB: 351° (WDS 2011) AC: 70° (WDS 2011)
Distance: 471 Light Years
Spectral Class: G0
Holy dueling triangles! This one you have to see to believe! It’s a classic triangle within a triangle.
To be more precise, it’s a perfectly shaped triangle sitting at the center of a larger perfectly shaped triangle — and the spacing is so precise that it looks like they were drawn in place by a celestial creature in possession of drafting tools. The sketch at the left by Jeremy Perez really captures what your eyes will be greeted with the first time they peer into an eyepiece at this gem. More of Jeremy’s sketches can be found at his website, The Belt of Venus.
On the night I made the observations described above, I wasn’t aware that Σ1659 was hovering just a short distance away from Σ1669. I came across it in the Haas book the next day, found the photo of it shown below in the STScI database, and then had to wait a couple of weeks for the skies to cooperate.
I found it waiting for me on a bright moonlit night with rather poor seeing, but even under those conditions, it was still a breath-taking sight. As you star-hop to it from Σ1669, you can’t miss this one in the finder — whether you’re using an 8×50 or a 6×30 finder, it looks like two barely separated stars.
Because of the bright sky background the only color I could see in the three stars was white. I found “C” to be slightly difficult, even with a six inch f8 refractor, but a few nights later under darker skies, this time with an f10 six inch refractor, all three stars really did a great job of decorating the view in the eyepiece.
To digress for just a few lines, the Stargate in the title of Jeremy’s sketch is a reference to the “Stargate” used by Buck Rogers (usually a configuration of diamond shaped stars) to travel from one location to another in interstellar space. So be careful about staring at this one for too long — you may suddenly find yourself in strange surroundings!
Σ1604 (STF 1604) HIP: 59272 SAO: 157111
Note: “C” is also HIP 59273/SAO 157112
RA: 12h 09.5m Dec: -11° 51′
Magnitudes A: 6.86 B: 10.0 C: 8.12
Separation AB: 9.0″ (WDS 2013) AC: 10.3″ (WDS 2013)
Position Angle AB: 89° AC: 10°
Distance: 72 Light Years (from Simbad)
Spectral Class: “A” is G4, “B” is K5
And now we’ll leap across a void of black space and — hopefully — find another triple system sitting in the center of our eyepiece.
Although, if your first attempt is like mine, you won’t.
Armed with my well worn traveling map, the trusty Sky and Telescope Pocket Atlas, I hunted and hunted, and hunted some more, for this elusive little triple on the moonlit evening of May 17th, and never really was convinced I had found the right star. I spent an hour trying to pry a likely candidate apart, but with no luck, even in the six inch Celestron f8 refractor. I was mired in a maze of haze, and the seeing was so bad I thought someone had attached an electric vibrating device to my scope — and the bright background sky contributed by a full moon wasn’t adding to my chances of success, either.
I was back the next night armed with the smaller sibling of the six inch f8, my Celestron four inch f10 refractor, plus the knowledge that the moon wouldn’t hit the horizon until 10:30 PM — which gave me less than thirty minutes to try again before the background sky began to look like daylight. At this time of the year, the sky still isn’t quite pitch black even at 10 PM.
I star hopped along the same path I had followed the previous night, which you can follow by looking at the last of the three charts above. Starting with Algorab, I moved to Eta (η) Corvi and then turned northeast for a distance of about three degrees to Σ1669, made a ninety degree turn and continued northwest a short degree or so to Σ1659, and then leaped across a void relatively devoid of stars — using the Hipparchus pair, sixth magnitude HIP 60595 and 6.5 magnitude HIP 60421 as guides — and landed again on the star I had been working so hard on the previous night.
And there it was …… right in the center of the eyepiece …… a tight little knot of three stars. I could swear it was even grinning back at me as if saying, “We were just fooling around with you last night.”
Two inches less aperture than the previous night and they popped right into sight …… just a bit surprising to say the least, but I’m not about to argue with success.
I bowed three times to the Sky Gods and went back to the eyepiece.
There were several things that definitely made a difference this time out. The black sky background was the main one. Even with its help, though, I still had to look closely to see the faintest of the trio — at a magnitude of 10.0 it hardly qualifies as a faint star in a four inch refractor. But it’s close enough to the 6.86 magnitude primary to suffer from some glare, and the 8.12 magnitude “C” component also contributes its share of glare. There was some haze once again, probably about the same as what I had looked through the prior night, but the seeing was about a full notch better — I’ll call it a “II” since the previous night didn’t even deserve to be rated as a “I.”
This is a very close grouping of three stars, and it forms an equilateral triangle that looks to be pretty close to dimensionally perfect. I carefully worked my way up from an 18mm Radian (56x) to a 16mm Astro-Tech Flat Field (63x) to a 14mm Radian (71x) to a 12mm Brandon (83x) and then to a 10mm Radian (100x). But at 100x I lost the faintest of the three stars to the haze, so I dropped back to the Brandon, and then settled on the 14mm Radian as the best of the bunch. By this time it was almost 10:45 PM, and I could already see the effect of the moon as the earth rotated it above the horizon. I watched for another half hour as the 9.4 magnitude “B” component faded out of sight, and then gradually its 8.1 magnitude relative followed it, although I never lost it completely.
These were just too far south and too mired in haze for me to see any color. Haas had a better time of it, as her description shows:
125mm, 50x: Grand! A broad triple star shaped as a triangle, made of three different colors — grapefruit orange, sky blue, and silvery nebulous. The bright primary is especially pretty.”
After reading her description, I returned the next night with my six inch f10, better skies, and an extra hour of darkness, and did much better. A 14mm Radian (109x) did the best job — not only was the faintest of the three stars visible, but I could just see a glimpse of color in the two brightest. There was a slight hint of reddish-orange in the primary, but the blue in the secondary was more noticeable. Again, a darker sky and a bit less haze made all the difference.
And that’s it for this trip through the northern section of the Crow ….. next time out, we’ll move a few photons to the north and search in the south of Virgo.
And you might want to invest in a good helmet for that one …………………… 😉
Stay tuned, Star Splitters!
(All WDS data updated 6/4/2014)