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Collimation of Celestron C150-HD reflector

Posted: Mon Feb 06, 2017 3:23 pm
I have a Celestron C150-HD with a lens between the primary and secondary mirrors (Bird-Jones design). I was hoping that someone could help me in collimation as the instruction manual is rather sketchy in this area.

When I look down the eyepiece hole without a lens I can’t see a reflection of my eye as I am sure I used to. Does this mean the primary or secondary is out of alignment? From various posts I have read it seems that the secondary is difficult to adjust so I will leave that for now, but will tackle the primary if it is possible.

I removed the lightweight plate at the end of the tube, covering the back of the mirror, to expose three Philips head screws; this is when I had a problem. The manual states that collimation is achieved by “loosening the three screws and adjusting the three knurled knobs until the secondary mirror is centered in the reflection of the primary mirror.” I can’t see knurled knobs and didn’t want to proceed without advice. Can anyone help?

Also I would like to remove the mirror with a view to it’s cleaning, I undid the six Philips screws on the outside of the tube end and assumed that this would free the mirror. Do I need to use some force to free it? Any help would be appreciated.

Re: Collimation of Celestron C150-HD reflector

Posted: Tue Feb 07, 2017 4:07 pm
by brian livesey
Hi Harry. You might get a better response on .