Beautiful Epsilon Lyrae Split
Posted 16 July 2013 - 10:06 PM
With my 8" reflector, the hallmark of very good seeing is a split or at least deeply notched 70x Epsilon Lyrae split. So so seeing would leave it elongated but notchless - still ok, but nothing textbook in the cards. Tonight was a text book night in Connecticut...
At 70x dark space was actually seen steadily between the low power airy discs. This is indicative of 8/10 seeing - something I haven't seen since last year. Boosting it up to 243x made the gap large and dark as you'd imagine and the diffraction rings were the perfect if nervous view. They were evident but still fluttery. Still, it was a brilliant sight.
My daughter in her late teens wanted to see what I was up to so she had her first double star view. Interestingly it became evident how its not too easy for a beginner or non astronomer to see the split. At 70x they appears simply singular. At 140x it was unclear but Im guessing her bobbing head and squinting eyes had a role in distracting a bit. At 243x it was obvious to her and she found it quite captivating particularly when I told her how these stars would look if we were on a planet in the system.
I want to say from there I dug into the treasure trove of other great doubles I even had in list form on Safari but my choices were killed by my primary mirror cooling vents hitting the altitude panel. My Dobson Hole is larger than ever now. This is fixable. Still I tried for 90 Hercules which would've been a done deal but I simply couldn't swing to it. Or the others in the hole.
Antares seemed the answer as it sat there low but its fluttering light down there was awful at 70x and ridiculous at 243x appearing to triple itself . I'm sure it was local seeing but nothing I could do about it.
I meandered around a bit and called it a night.
Posted 17 July 2013 - 10:38 AM
Posted 17 July 2013 - 03:11 PM
I can regularly get x6 in my 4" refractor. Sometimes, very rarely, I have seen split at x51.
Never got below x100 with my 8SE- just too bright.
Posted 17 July 2013 - 07:26 PM
The thing that made this happen was the dumb luck of a mirror naturally being at ambient air temp and no tube thermals or boundary layer. I did think my new boundary fan would be the first to pull this off if it were doable but Mother Nature beat me to it! I've NEVER had a light path do clean of thermals .
Views in the past - even with better seeing had stars fatter at low power due to a rear fan or no fan leaving the boundary layer intact and swelling the stellar image jjjjuuuussstttt enough to close the 70x dark space gap and make the doubles look like a classic Dawes split.
I credit this to the serendipity of natural thermal management. I still can't believe it actually.
Posted 20 July 2013 - 11:45 AM
I don't use any fan on my 8 inch F/6 ''Toleascope'' Dobsonian and the smallest magnification I can use to split the Epsilon 1-2 Lyrae ''Double-double'' is 93x,using a three element ''all-cemented in one piece'' eyepiece of 12.8mm focus created by me friend Silviu,we use to call it SS or Solid Simetric, the Tolles version of the Possl eyepiece.It have only two air-to -glass surfaces.The stars of the Double-double are too bright in this telescope at lower magnifications.
Instead,using the same eyepiece on my 3 inch F/9 ''Optus'' Newtonian ,an older type of Lidl telescopes ,the Double-double in Lyra was split Thursday this week at only 55x /Solid Simetric 12.8mm ocular.The Airy disc of each star was clearly visible,with a very thin but consistent black space between them.
If I would be an 8 inch reflector,I would feel very offended! :bangbangbang:
Posted 20 July 2013 - 03:28 PM