I purchased a meade 127ed on amart awhile back and have been learning how to collimate and center the lenses. I have done quite a bit of star testing on this scope and I am puzzled with the results. To begin with the scope does have some astigmastim which rotates 90 degrees from inside and outside focus. I think the images I get of jupiter are fairly good but my infocus high power star images are not what I would like. Stars are not a round ball with diffraction rings around it. Sometimes it is round, then elongated, and sometimes little spikes. I have a 76mm scope that has some astigmatims as well, maybe worse than the meade 127ed but still give a nice high power image of a star, round with a couple of diffraction rings around it. So I would think the Meade should be able to do that as well.
Anyway, I do star tests with and without a diagonal. at powers from 266 to 342x. I have done most of the testing on nights of good seeing, and use different stars, mostly altair and vega. What I see outside of focus is some color within the rings but concentric rings, well defined with a bulleyes in the middle. Inside of focus I don't see the color, and the rings are still fairly well defined but not as defined as the outside of focus rings, but the puzzling part is that the bulleyes is not centered inside of focus, it is off to one side. I have collimated and centered the lenses many times I cant seem to improve the off center bulleyes. If it was a collimation or centering issue wouldnt it show up in both the outside and inside star patterns???
Thanks for your help.