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Algieba – a new star for the Dolphins!

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
Separation          4.4″
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.

Algieba is easy to find. It’s a second magnitude star about 8 degrees north of Regulus in Leo’s sickle. (Screenshot, with labels added, from Stellarium.)

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.

Glowing in gold, and always a glorious sight to behold! (Click for a larger view).

Glowing in gold, and always a glorious sight to behold! (Click for a larger view).

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3 Responses

  1. Yep, I see the green, too. This is really a great example of how the color of closely spaced stars is affected by contrasts.

    This is also one of my all time favorite doubles. Every time I turn a scope on Algieba and watch those two colorful pinpoints of light come into focus, I feel like a starved Star-Splitter at an all-you-can-eat buffet.

    But then some double stars just always have that affect on me. 🙂

  2. Aha! A clear sky this morning!

    I checked the sky at midnight and saw that it was still cloudy, but knowing the forecast called for clearing, I turned in and decided to check back later. At 4:30 I got up and took a peek out the window and could see a beautiful crescent moon low in the southeast – checked another window and I could see a sky full of stars!

    The temperature was a very cool 31 degrees, which meant the deck I observe from was coated with ice from the moisture that fell earlier in the night. So I grabbed a 60/800 refractor that was sitting on my Unitron alt-az mount and headed out into the drive instead.

    The moon was up, Saturn was easy to pick out, Arcturus and Izar were calling to me, but over in the southwest I could see Leo – and above Regulus, I saw my target – Algieba!

    Even a 60mm lens needs to adjust to a thirty-five degree difference in temperature, so I gave it some time to cool down while I scanned that beautiful dark sky. After about 15 minutes, I dropped a 20mm TV Plossl (40x) in the focuser and waited for the image to settle down a bit, but couldn’t quite see a split. Out with the 20, in with a 15mm TV Plossl (53x), and I looked again. A bit better, but still not quite what I had in mind. I did notice that the seeing was erratic – moments of very good followed by totally out of focus.

    I reached for a 10mm Celestron Plossl, but by mistake grabbed the 6.3mm version of that series, which jumped me all the way up to 127x. I turned the focus knob quickly, then slowly as the image began to sharpen, and managed to get a somewhat focused pair of stars. I waited a few seconds for it to get better, saw a slight improvement, and then looked at the barrel of the eyepiece and realized my mistake. I stayed with it a bit longer and managed to coax a couple of diffraction rings from each star, but finally decided to use the 10mm (80x) instead.

    Much improved! I finally got what I was after – two sharply defined globes with a very small slice of dark sky between them and the surrounding diffraction rings. Really a rewarding first view of Algieba for this winter!

    But Saturn was calling me, and I saw a few clouds moving that way, so it was time to make a quick move before it was too late.

  3. Had my first view of Algieba for the fall of 2011 at 6:30 AM this morning, just as the sky was beginning to get pale blue — looks like about a month earlier than last year, judging by the date on the comment above.

    A 76mm f/15.7 Tasco, a 10.5mm Ortho (114x), a pale blue sky for a background, two sharply defined stars with traces of gold and yellow, surrounded by crisp diffraction rings ………….. if there had been a way to slow the earth’s rotation and hold back the daylight, I would have done it right then and there.

    There are some moments that deserve a monument with the date and time carved into it — and wow, this was definitely one of them.

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