Quote: have noticed slightlt oval star images just inside and outside of focus,
-DannyMy warehouseMy Channel
Quote: Quote: have noticed slightlt oval star images just inside and outside of focus, did the oval shape turn 90° from inside to outside focus?does it happen with short fl eyepiece?
Quote: a flat secondary only has to have a bit of power to show astigmatism in a 45 degree orientation.
Quote: It is the difference in depth along the two radii that induces astigmatism, not the surface P-V error itself
Quote:After trying almost everything to sort this out,convinced it was my secondary that wasnt good,i took the mirror off the holder and remounted it with new silicon,collomated and waited on a clear sky, and would you believe it, sky clear as a bell tonight.Set the scope out to cool,then turned the scope on Jupiter and couldnt believe what i was seeing,perfect focus amazing detail even inside the red GRS!The moons actually showed as tiny discs,so to celebrate just ordered my self a 11mm 82 E.S eyepiece.Thanks for all the help and advice people.Paul
Quote:...i took the mirror off the holder and remounted it with new silicon...
Quote:Is there any test that i can do to tell if my secondary has astigmatism.