Pushing my limits with AS80
Posted 18 August 2013 - 04:29 PM
yesterday there was a strong haze and quite bright Moon so I decided to test my skills on tight doubles with 80mm refractor. I had out my old uncoated Zeiss AS80/1200 from about 1930ties. I was also using Baader Zeiss prism.
I started with pi Aql (6.3+6.9, 1.4") which I already knew that I can split with 80mm lens. This evening it was also very good and clean split at 170x and 190x. I could see two nice touching discs at PA~120deg. There was a hint of some darkening between. The view was very encouraging.
Next stop was tougher mu Cygni (4.7+6.2, 1.9"). I could see small star in the 1. difractive ring at PA~315deg. It required some concentration.
Next on the list was STF2780 in Cepheus. I just vaguely remembered that it was difficult one. Indeed it was (6.1+6.8, 1.0"). All I could see at 170x and 200x was small bump at PA~210-240deg. It was even difficult to judge its position but it roughly agrees with correct one.
The last one was even tougher pi Cephei (4.6+6.8, 1.1"). The main component was very nice orange star. There was almost no sign of its companion. But from time to time I could glimpse with averted vision something strange going on at PA~0deg. Oddly enough, I found out later at home that this is about the correct position.
Posted 18 August 2013 - 09:45 PM
Posted 19 August 2013 - 07:52 AM
I'm saving this to add to my own list - very well done and told.
Those last two sound like very difficult doubles to make out but you did it. I tried some elongated doubles the other time out but the seeing was elongating it in its own way so my attempts were dashed. Again very impressive results here Alex. I don't think Ive pushed my 70mm much beyond 2.5" and not because it can't - its a beauty - but I've been a little relaxed with its doubles *diet* .
I truly enjoy your cutting edge observations!
Post edit: Sky Safari doesn't recognize STF2780 - it merely skips over it. In putting the SAO number merely gives me an 0.1" double at 5.9v. They omit every once in a great while. See pic attached. Going to the Stella Doppe site however clarified all. Nothing's perfect!
Posted 19 August 2013 - 02:14 PM
Posted 27 August 2013 - 02:33 PM
BTW, in May I noticed in 63mm refractor that pi Cep is elongated at PA~0deg without prior knowledge about the secondary star position. That is why I wanted to check this tight unequal double in 80mm. Paradoxically, I was observing pi Cep last year in larger 110mm and 130mm refractors. I could not see even a hint of the secodary.
Posted 27 August 2013 - 10:28 PM
Seeing elongation on this double with 80mm is very good. If the 63mm Telementor hinted at it being double that would be pretty much a "limit" observation (~0.5R) for an even double, and this one isn't. I'd expect the seeing to be very good for that to be possible.