Expert: Paul Wagner - 12/3/2008

Question
I have a commercial refractor telescope and i don't know which is the focuser
i want to use the focuser for the telescope i'm going to build
and i have to know its height to know the diameter of the diagonal i'm going to use.
So can you help me

Answer
HI Hady

nice to hear from you  again! The focuser is that part of the telescope the holds the eyepiece--it can move back and forth so  that the telescope can focus on your object.  But a refractor focuser usually has a flat disk at the end closest to the lens, and that's what you would have to attach to the side of your telecope tube.  Because it's flat, you  will have to adapt it in some way to fit the tube.  The height will be the distance from the flat disk at the end of the focuser to the end of the eyepiece tube.

Paul Wagner