[Vader (Valery)]

Originally Posted by celstark

I've looked long and hard at those results and they really are just plain ugly. FWIW, the fact that they are ugly has been discussed over on CN and that thread wasn't pulling any punches either. There's been another test of the scope that had it fare a bit better, but still not great:

http://74.125.91.132/translate_c?hl=en&sl=de&u=http://www.teleskop-service.de/Testberichte/cassegrains.gso.rc.200mm.php&prev=/search%3Fq%3Dgso%2B8%2522%2BRC%26hl %3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-USfficial%26hs%3DIA0&usg=ALkJrhhd fFj20i2M200RONh17AmH_sT6Yw

There, the P-V ended up at 1/3 wave and the Strehl at 0.89. To my untrained eye, it looked worse than a Strehl of 0.89 would indicate.

Craig

It is quite obvious, that reference points at this interferogram were not
correctly placed. They were manually placed with intention to smooth down interferometric fringes - this makes final figures better.
I can bet for a lot of money, that if I will process this interferogram with
our professional software with 5-8K reference points placed automatically,
the results will be not better than Strehl 0.6 - 0.7.
This is not totally crap, but very poor. If we consider a large central
obstruction, then a real Strehl will be 0.5 at best.


As for star images during long exposures. This effect is even more
visible in large professional telescopes. However, I don't remember
even one order for professional optics with technical requirements
lower than about 0.9 Strehl.
As better your scope optics, as better star images you will obtain under
similar conditions.

As for the picture of galaxy given at that page. Too small scale for
such a long focus.