OK here's the background. I'm a beginner, or amateur amateur as I like to call it. I have a Celestron C-9.25 on a CGEM. Both were purchased used (here on Astromart). I knew I was going to have to collimate this scope after it was shipped to me, so it was no surprise that saturn looked very blurry upon my first sighting. This was with clear skies with decent viewing, and very little light pollution. I knew it had to be done.
I got a few more EP's and a Barlow so I had more choices in magnifying power. So I have tried to collimate this thing several times now, but I'm having trouble with the diffraction rings. As in, I can't see them very well, and when I use the higher power EP's, it just gets more difficult beacause the rings get blurry and closer to the outer edge. The rings just don't seem to be appearing in a concentric pattern, and are poorly defined. This makes it impossible to use them to center the CO. It actually seems easier to center the obstruction shadow at low power since the edges are sharper. I have tried using the following EP's: Celestron E-lux 25mm Plossl. Baader Hyperion-Aspheric 36mm. Baader Hyperion 8mm MC. And, Celestron 8 to 24 Zoom (#93230). I've tried all of these with and without a Meade Series 5000, 2X TeleXender in place. All in a Celestron 2" Star Diagonal (#93527). This is all with stars of varying intensity (tried a bunch). I can see the rings slightly better on the infinity side of focus, but not well enough to use. I will say that the focus assy seems to be VERY sloppy on this unit, but a can still get a very fine focus with a light hand. One other observation. The eccentricity of the shadow seems more pronounced on one side of focus than on the other. I can't remember which though. I have tried this while wearing my contact lenses, with my glasses and without any correction at all. The problem seems to be consistent over these scenarios. So what's going on here? Is there something wrong with the scope, or is it something else? I'm at the end of my rope with this deal. :C
I got a few more EP's and a Barlow so I had more choices in magnifying power. So I have tried to collimate this thing several times now, but I'm having trouble with the diffraction rings. As in, I can't see them very well, and when I use the higher power EP's, it just gets more difficult beacause the rings get blurry and closer to the outer edge. The rings just don't seem to be appearing in a concentric pattern, and are poorly defined. This makes it impossible to use them to center the CO. It actually seems easier to center the obstruction shadow at low power since the edges are sharper. I have tried using the following EP's: Celestron E-lux 25mm Plossl. Baader Hyperion-Aspheric 36mm. Baader Hyperion 8mm MC. And, Celestron 8 to 24 Zoom (#93230). I've tried all of these with and without a Meade Series 5000, 2X TeleXender in place. All in a Celestron 2" Star Diagonal (#93527). This is all with stars of varying intensity (tried a bunch). I can see the rings slightly better on the infinity side of focus, but not well enough to use. I will say that the focus assy seems to be VERY sloppy on this unit, but a can still get a very fine focus with a light hand. One other observation. The eccentricity of the shadow seems more pronounced on one side of focus than on the other. I can't remember which though. I have tried this while wearing my contact lenses, with my glasses and without any correction at all. The problem seems to be consistent over these scenarios. So what's going on here? Is there something wrong with the scope, or is it something else? I'm at the end of my rope with this deal. :C
