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View Full Version here: : Cassegrain Primary, I messed up, Doh!


glend
01-05-2020, 09:30 PM
I am kicking myself for touching those screws, on my GSO 8" Classical Cassegrain. Ghosts of RCs past have come back to haunt me. It was fine The way it was, a week old, nice star test out the box. Stupid me decided to install a collimation ring (because it uses the same back plate and focuser as the RC model) and i installed it today. Initially things were going fine, then i touched the primary, just to tweak out a touch of optical misalignment. Things went to hell then, and i soon found myself back in the endless repititions of fix one thing and bugger something else up.
I tried research, built a light up target box to reflect the donut to do optical alignment, used lasers, Barlowed lasers, Cheshires, everything in my toolbox. I am missing something. Trouble is there are not many of these scopes out there, so no direct references to call on.
I need to go back to basics here and just get that primary back in alignment. Any suggestions?
:shrug:

multiweb
01-05-2020, 09:47 PM
To recenter your primary you would need to put your scope in a rig and use something like the hotech laser board for the initial mechanical alignement otherwise it could be a lot of trial and error. Once you have your primary close you can start tweaking the secondary then iterate back between primary and secondary until you get everything aligned.

glend
01-05-2020, 10:08 PM
Thanks Marc, I think I have got it back. I have gone to the Orion Collimation instructions, which Doug sent to me, and it was not as far gone as I had feared. Nearly finished now. Thanks for your reply.


Update: all done, perfect now. Did a star test as well.