A couple days ago I decided to do some work on the early (I guess, s/n 9136) orange C90 I got with the C8 trunkful package I picked up about a month ago. I collimated the finder and did a star test, that showed rather rather dim images (same with daylight: maybe the mirror shows its age?), and moderately offset Airy disks. Since the focuser mechanism feels totally dry and is quite loose, to the point that it wiggles a bit, I thought that greasing the threads may help to line things up a bit better.
Based on these instructions ( http://www.astronomy...um.com/c90.html ) , I expected to find two focuser retaining screws under the adapter foot, but there is actually none. Evidently there was a different design earlier on.
I noticed a small set screw where indicated by the screwdriver tip, that was fully seated and felt very loose. I tried to unscrew it but it does not seem to retain the focuser. I decided to screw it back and....it fell inside.
So, the question is, how do I get to it now? Thanks