Telescope Reviews: Short evening with doubles

I had another short one hour session with AS80/1200 last night. Following the idea of Sissy's project, I was trying to investigate tight unequal doubles. Seeing was much worse than previous night. Airy discs were clearly visible but jumping, I would judge it as Pickering 5-6/10. Definitely quite bad for 80mm lens.

Even under those conditions I was able to split again pi Aql (200x). I tried as well mu Cyg (200x). It was much harder than previous night but still without doubt doable. I checked delta Cygni afterwords. This time it was not definitely routine. It was much harder to spot than mu Cygni. I had to really fight to see it. First, the star was just in zenith which is always troublesome position for alt-az mount. Second, it took me several minutes of precise focusing (in f/15!) before I started seeing the companion in short periods of time.

Then I tried another star from Sissy's list, 23 Aql (5.3+8.3, 3.0"). I split this star last year in ED100 when I accidentally run on it. It was difficult split already in 100mm refractor. Yesterday, in 80mm at 200x, it was even more difficult. Very faint companion was popping in only for tenths of seconds. But I was persistent and I managed to have few seconds clear and stable view of the secondary. I estimated its PA~10deg which I later found out to agree with correct position. My feeling was that I'm limitted not by the resolution but by faintness. Bright sky with almost full Moon was not helping. Another interesting fact is that when I switched to higher power (235x - Pentax XO5) I could not glimpse the secondary at all. It is true that I did not spent too much time at it with this eyepiece as with CZJ O-6, but I could not even get those tenths of seconds occasional glimpses through Pentax XO. May be it was too much of magnification for such bad conditions.

Finally, I tried STF2878 in Pegasus (6.9+8.1, 1.5"). At 200x, I could see nothing but ordinary star. At 235x, it was still just a star with very faint and difficult to see small tail which was roughly following the star. Later, at home, I found that PA is indeed 117deg (I like that PA is not listed in Cambridge double star atlas which I'm using in the field; I can use then estimated PA to confirm the split). I don't consider this double splited even if I guessed the position. It was just a guess and the view was not stable and clear enough. I think, the problem here was again faintness of the secondary. I need to find another candidate with delta M~1 and 1.5" separation.

Edited by Sasa (08/30/12 05:01 AM)