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#1 magnus

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Posted 31 January 2013 - 07:10 PM

At last the sky was clear and I had pretty decent seeing ca. 8/10 on good moments.I did some observing in Leo which was in good position from my balcony.The scope I used was my old -73 orange C8 on an CG-5 with single axis drive.
Iota Leo was split at 171X and very nice in 320X.
Gamma of course a wonderful gem in 133X.
I decided to a have try on omega as I have never observed it before. At 240X I could just barely make out a sort of elongation in E-W direction. At 320X I knew for certain I"had it"; I could make out two distinct airy discs just touching. At 480X and 576X I had a split with dark space between the discs. Very nice.To me both discs were white.

Karkoschkas Observers Sky Atlas says 5.9-6.5 mag. And sep 0.8" -15 Can`t find anything `bout this binary in Haas book (strange)and I really do not get much when googling.

Surely many of you here has observed this nice and easy to find double. Could you share your experience with me, please.

/Magnus 57N.

#2 fred1871

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Posted 31 January 2013 - 08:08 PM

Magnus, Omega Leo is listed in the Haas book - but only as "2 Leo". It's also STF 1356. The Cambridge Double Star Atlas chart shows it as Omega and with the STF number.

Current WDS listing has magnitudes of 5.7 and 7.3 (same as Haas gives - her source was earlier WDS) but it's a binary, now gradually widening, and WDS gives a 2011 measure of 0.8". That also fits the ephemeris in the 6th Orbit Catalog. The period is 118 years (unhelpfully given in days in the 6th OC!). The Haas book quotes Smyth on colour, with "pale yellow, greenish..." but Smyth's colours are not always reliable (understatement).

My only (fairly) recent observation of Omega Leo was in April 2011 with my 140mm refractor - a bit less aperture than you used! But there was a hint of elongation at 160x in good seeing, and at 400x it was a clear figure-8 double, two discs in contact. I was pleasantly surprised, given the brightness difference of the stars. The WDS magnitudes are double-decimal, which with brighter stars usually means Tycho numbers, so they should be quite accurate.

That's less than 2 years ago, so the difference in separation since then is minute,and what you describe with 8-inch (20cm) aperture is what's to be expected, separation at high power. The benefit of more aperture.

Colour? I saw the pair as slightly yellow in tone. That also fits the spectral type, F9 for the primary. The stars will look brighter with more aperture which with some stars seems to reduce colour effect, though that's a debated issue. :grin:

#3 magnus

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Posted 31 January 2013 - 11:47 PM

Thanks for your feedback. Found it now in Haas book; with the components mag. 7.3 and 5.7 (1.6 mag difference)I am also plesantly surprised I could split this binary. But as I wrote I had good seeing and of course the C8 spot on collimated!

Later in the night I had a hard work barely elongating zeta Boo at 576X. 3 years ago I had a defenite split at 480X and 576X with my 8"f/6 OOUK Newt. But that`s another story....

/Magnus 57N.

#4 WRAK

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Posted 01 February 2013 - 03:06 AM

Magnus and Fred - very interesting observations. As delta-m is not this big I would have expected it with relation to the Dawes criterion an easier split with the C8 and a bit more difficult with the 140mm refractor.
Wilfried

#5 Rich (RLTYS)

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Posted 01 February 2013 - 06:21 AM

With my 10" refl at 506x both stars appear a warm white color.

Rich (RLTYS)






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