Can Not Focus My Refractor

[refractordude]

Hello there


It is the Celestron 150nn F8 achromatic. I did a front/back focus star test and got a complete circle, but only one outer inside ring. I notice when I turn the focuser forward it will go back a very little on it's own. I was bringing objects to focus by just turning the focuser backwards to get a sharp focus. Yes the telescope, diagonal, and eyepieces were all acclimated to the outside temperature.


I can bring stars close to focus. Thanks all

[The Mekon]

Mirror or prism?

If you are using an 1.25" prism the focal path may be too short.

A 2"prism usually has a shorter path than a mirror.

Telescopes these days are made with very short tubes and you will find that good focus is near the end of travel.

[JohnF]

An having some trouble with my 150mm F5 Skywatcher. Cleaned the Lenses, wondered if I put them back the Wong way ??

[refractordude]

It was the focuser and I am glad about that. Added the stock focuser and all is now good. Just need to grease it up a little.