Wednesday, September 18, 2013

Troubleshoot Prime Focus on 60mm Refractor (It Finally Works!!!)

In an earlier post I wrote about buying my first t-adapter to try to hook my camera up to my 60mm Meade refractor. The basic problem was that I couldn't reach focus even though all the pieces fit properly - the issue being that I had the focuser all the way up against the optical tube and was still not quite focused. I had to find a way to shorten the length of my adapters to give myself more room to focus.

I bought a .965" to t-thread adapter and was initially shocked with how big this thing is! It looked a lot smaller in pictures. This adapter was longer than the t-adapter that slides into the eyepiece, but I thought maybe since I could do away with the diagonal mirror it would still be short enough. (I was wrong).

I took my telescope and my entire set up to an Indiana Astronomical Society event to try to get some guidance. I was able to borrow a Barlow lens from another member, which seemed to help but I still couldn't quite get to focus. I had to daisychain all of these adapters and eyepiece cups together and it was still too long.

The next day I took a more critical look at the pieces that I already had to work with. I was pretty sure that I already tried every combination of pieces that came with my adapters, and I remember laying them all out on a table to see if I could get it to work. With fresh eyes I noticed that the smaller and of the .965" adapter unscrewed and I thought to myself the threads must be T threads because the entire tube is the same diameter.

canon telescope prime focus adapter pieces
Camera body --> T-ring --> T-thread to .965" --> .965" threaded collar

.965" to T-thread camera adapter (too long, I used just the piece on the left)

canon telescope prime focus adapter pieces
Collar screws onto the focuser tube and slides over the .965" male

canon telescope prime focus adapter
A look at my prime focus setup. I was in focus at this distance (with an inch or so to spare on the focuser)

canon telescope prime focus adapter
Prime focus in the field (I was so pumped!)
I went outside with this super short configuration and what do you know, it works!

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