C9.25 loose secondary - help required!

[Johnboy2011]

I noticed recently I just couldn't hold collimation and then noticed that the secondary was loose! There was a small amount of movement from side to side and I found that I could rotate it freely. By turning clockwise It seemed to tighten so I did this and crossed my fingers and at first it seemed ok. When using it for visual on Sat it was ok at first and then when I slewed across the sky collimation went way out.

Does any one in the know have any ideas, I am out of my depth?!

Thanks,

John

[E621Keith]

Can you post a picture of your C925's secondary. There are several versions. On some models the secondary mirror is removable for Fastar lens while on others the secondary mirror is bigger than the clearance hole in the corrector plate and not removable as a result.

[Johnboy2011]

Thanks Keith, photo attached....

It is one of the older US made models and I don't beleive it is Faststar compatable.

Thanks for your help,

John

[E621Keith]

I'm afraid my C925 is the newer model with a different secondary, so I won't be much help. I'm sure others who own similar US model will be able to help you.

[Johnboy2011]

Someone out there must have some ideas......?!!

[dweller25]

The secondary can be tightened up - CAREFULLY - by rotating the outer knurled black collar clockwise - CAREFULLY......;

[Peter Drew]

Try and make sure the secondary mirror does not turn as well whilst attempting to tighten the locking ring, the mirror has a preset orientation.

[Plantins]

Tighten the collar as already mentioned and re-collimate.

Also when collimating make sure you don't turn any of the Bobs Knobs too far anti-clockwise as this will unscrew it from the secondary and perhaps make it loose.

[eid]

Try and make sure the secondary mirror does not turn as well whilst attempting to tighten the locking ring, the mirror has a preset orientation.

Since the secondary has been moved side to side, it also needs to be centered in relation to the front casting so it matches the primary's position, (assuming the primary is actually well centered). A vernier scale is very useful for this. I'm not sure how much difference this actually makes though.

I was recently in the position of having stripped down my C9.25 including removing the primary housing from the corrector. With careful realignment of all the components in relation to the housing and eachother, the rebuild went well and now performs better than it ever did before.