Dave, coma is never present in the very center of the field. If you see problems at high powers, dead-centered, you don't have coma, but someting else. The halo description sounds like spherical abberation. --- DunnDave@aol.com wrote:

Brent, Chuck and Dave, Thanks for the comments. I probably ought to have you look at it with me. I am able to get round stars with flares. When I attempt a star test it looks round when the collimation is correct. This makes me wonder what I am seeing. I see the problem at it's worst when viewing a bright star or planet. For example, I was 78 - 406X. I could get a good focus on the planet and could see good surface detail. The planet was surrounded by a halo of light that seemed to be oscallating, possibly by my eye moving around. Bright stars never appear to come to focus even when other stars appear to be points. When I first set up the scope at Monte I discovered that the secondary was not centered in the tube. Since I used a laser to collimate, I was able to tip both mirrors and get good images of galaxies and nebula. Stars and planets were awful. I have fixed the allignment problem and now just have the halo, which I think made Mars look like a comet with a big nucleous.

Dave

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