Celestron 130 SLT Astrophotography Modification
Reflector telescopes are the only option for large apertures. Refractors are quite costly over a couple of inches. Newtonian reflectors have many advantages including simplicity and low cost. One major drawback of the Newtonian telescope is the focal point often falls short of a T-mounted camera making prime focus photography impossible. If you don't know what I am talking about, here is a good explanation. Two common methods of making Newtonian scopes work are cutting your Optical Tube Assembly (OTA) down or use a Barlow lens the has a low setting lens. Hacksaw to my telescope scared me. Using a Barlow all the time seemed very limiting. In comes option number 3! Extend the mirror adjusting hardware to move the mirror forward.
I made a trip to the local big box hardware store and found every thing I needed for a few
bucks. The knurled knob and spring on the bottom of the photo are the original culmination adjusting hardware from the primary mirror holder. On the top, left to right are aluminum spacers, cut off bolts and nylon spacers. All are 1" long. I ran a tap through the hollow aluminum spacer to thread it the same as the cut off bolts and the knurled knob.
Bottom left and working counter-clock wise: the original stud in the back of the primary mirror, the aluminum spacer and cut off bolt threaded onto the stud, and the nylon spacer slid over the aluminum spacer. The original spring will perch on the nylon spacer and the cut off bolt is the
same length as the original stud. This moved my mirror and focal plane forward one inch. Now the camera can focus at prime focus. I need to use a one inch eyepiece extension for very low focal length eyepieces, but that was a cheap and easy fix.