That’s the Miami Dolphins football team – they could use a new star this year – but that’s not my department. My department is trying to describe the elusive and lovely colors of γ Leonis, aka Algieba.
Algieba – Gamma (γ) Leonis
RA: 10h 20m Dec: +19° 51′
Magnitudes A: 2.2 B: 3.5
Position Angle 127°
Distance: 90 LY
Spectral Classification: K0/G7
A few mornings ago I was sitting in the glare of a nearly full Moon, looking at Algieba for the umpteenth time and wondering how I would describe the colors I was seeing and the Dolphins distinctive orange and green leaped into my head. At least that was how they struck me with the 8-inch Celestron EdgeHD under average – maybe a little below average – seeing. With a 60mm F13.3 Tasco I had more trouble seeing the color. The orange tint was there for the primary – but I think the green was in the secondary primarily because it was already in my head from the view with the larger scope!
My difficulty in picking up the color this time may have been due in part to the glare from the Moon because usually these colors jump out at me. Actually, as I think about it these colors may be more impacted by the Moon light than those of other stars because these aren’t real – or the green certainly isn’t. Well – it’s real enough to me and selected other observers, but as the “The Night Sky Observer’s Guide” by Kepple and Sanner explains, the two stars are really deep yellow and pale yellow. “Some observers have reported the companion to be greenish – but that is at least in part an optical illusion caused by the contrast of the deeper yellow of the primary with the paler yellow of the secondary.”
The “apparent color” of a K star is “yellow orange” so that roughly fits my description for the primary. But the green of the secondary? A G star should be yellow. ( See the chart in this post on Star Colors.) Sissy Haas apparently used a 60mm and writes: “A brilliant figure 8, slightly unequal, grapefruit orange in color.” She quotes Smyth as describing the stars as “bright orange, greenish yellow” and Webb as “Gold, greenish red.” Oh boy! So the green business is persistent, but not entirely consistent! What do you see? This one is really in the eye of the beholder, but beautiful however you describe it.
It is simple to find and not a difficult split. To find it, look for the second star up from Regulus in the sickle of Leo. I know I have the right star when I look in the finder or low power eyepiece because 40 Leonis, a 5th magnitude star, is less than half a degree south of Algieba at about PA 189°. And since the PA for the secondary is 127° this give you a rough guide as to where to look for it. (If sky directions and position angles confuse you, see this post.)
I split it easily with a 24mm Panoptic (83X) in the 8-inch SCT. I liked it best in that scope with the 13mm Nagler (154X). I also had no trouble getting a clean split with a 60mm refractor. That done I was encouraged to try again with the 50mm Little Rascal. The night I did most of the tests on that scope for this post I wasn’t able to split Algieba with it. But on this particular morning – the one after the lunar eclipse – I did split it nicely using the 3mm click-stop (68X) on the 6-3 Nagler zoom. This meant seeing was better than I first thought – so I went off to try Porrima with the 8-inch. I really would like to get a pristine split of that pair!
It had been hopelessly cloudy here for the total lunar eclipse on December 21, 2010 so, of course, the next night it was brilliantly clear and I marveled at the brightness of the snow-covered landscape reflecting the just-past-full Moon’s light as I approached my small observatory. When I emerged from it a while later – I had no real luck with Porrima – I was brought up short by clouds near the Moon. Yes, I’m conditioned to abhor clouds – but these were gorgeous. Light, stranded ones sailing in from the northwest and all shining brightly in the moonlight. It was a Christmas scene out of Currier and Ives. Home, fir trees, snow on the ground, friendly clouds above and the Big Dipper high over head with Venus, fairly screaming for attention as it rose in the southeast and shone through the bare trees in my neighbor’s woods.
You split some, you don’t split some, but you always win just to be out on nights such as this.
Note: A few mornings after this I was out with the 50mm F12 Tasco to tackle Mizar and once done, I took on Algieba and then Castor again. On Algieba I got a split with the 10mm Tak Le, but it was much better with the 7.5 and it wasn’t until I put in the 5mm (120X) that the colors really came out.