[Hemi]

I’m into my 4th year of Astronomy, but firmly a newbie.

My C925, is now 4yrs old as well. It’s been used a lot, but never needed much TLC. Whilst getting to grips with my new eq mount and the fun of polar alignments, I noticed that my collimation was off. I went to the front of the scope and noticed that my corrector was very dirty.

I looked for the collimation screws! They were hiding under a rotatable plastic cover, that did not rotate very well. What did rotate however, was the entire secondary housing! Gulp and panic! The secondary housing was loose! Not just the retaining ring but the assembly! Turning it would turn the orientation of the collimation screws!

Stopped, and closed my eyes and guesstimated the original position! And googled. My patients google (and it’s generally not that helpful) but we astronomers google for answers all the time!

Googling got me answers that ranged from, the world is going to end, to relax dude and get a beer the suns still coming up tomorrow, no problem.

Any how, after a lot of cogitation, I went back to the scope....with courage and fortitude, I tightened that secondary retaining ring! Luckily it caught and did not spin! (Otherwise the corrector needs to come off I’m told). I took off the visual back, and looking in from the front and back, all seemed grossly lined up. Put back the diagonal and 12mm EP and focused on Antares......the collimation was totally screwed now. But that was it! Only collimation.

So I learnt how to collimate my SCT, it was a bit random but projecting your finger at the narrowest point of the concentric rings definately helps identifying which screw to turn. I don’t think it’s perfect, but I think I will uses a camera for that.

Sorry for the ramble, but to summarise my experience and my googling.

A rotating secondary on a sct is not much to worry about, it is a rotating corrector that is! It will mess up your collimation sure, but collimating an sct is easy! Just takes a little time and care, the Internet posts are correct in that you only want 1/8 turns, no more, even if you feel it’s not doing much.


Clear skies

Hemi