I am a new member. I just appended a response to an old forum regarding Coulter Collimating Eyepieces, but maybe this over 5 years old? Sorry, I think I just need to enter a fresh post in my case.
I have a CT-100 (4" F3.5) and a 10.1" Coulter Odyessy Compact Dobsonian. In both of these Coulter scopes, the secondary mirror is permanently fixed and cannot be adjusted. I just have the 3 primary mirror adjustment screws to toy with in both cases. I have the Coulter Collimating Eyepiece kit discussed in that old forum. It seems okay. I have not used the Ronchi screen for collimating yet, only the peep hole. With the CT-100, once I center the diagonal, I decentered the diagonal reflection with a quarter counter clockwise turn per the instructions from 1979.
But I was wondering if a laser collimator would work on these two Coulter scopes, since the secondary mirror cannot be adjusted and the diagonal reflection needs to be decentered per Coulter's instructions. Any Coulter owners out there with collimating experience with these scopes?
BOTTOM LINE: Can these two scopes be OPTIMALLY collimated? But with either a Laser Collimating Tool or absent that, a simple Cheshire Collimating tool, remember, the FROZEN secondary mirror will shortchange perfect collimating adjustments. Maybe I just need to go back to the original Coulter peephole eyepiece, center the primary secondary image, then back off to slightly decenter the seconadary image as Coulter alliued to 30 years ago?
Is there any to her approach. Unless I find a good mirror specialist, I really don't want to put a CENTER SPOT on either mirror. But do I have a choice.
Both these scopes are aimed at resolving Omega Centauri from the Southern California deserts. I took the 4" Coulter CT-100 Tahiti in 1991 to see it. Could not resolve that glob with either the 25mm or 6 mm Kellner, which was supplied. Maybe if I had a 32 mm Televue Plossl or an 11 mm Televue, things would have been different. And the 10.1" Coulter Odyssey Compact could not resolve it either from Borrego Springs, California on several occasions. True, OC was 10 degrees above the southern horizon, but I could not see individual stars, only what appeared to be fine dust or haze, albeit LARGE.
So with so many observations of Omega Centauri proving negative with two able telescopes, it has to be a collimating issue, right?
Any feedback will be appreciated!