Hi all
I have a Celestron c9.25 XLT for planetary imaging but thought i'd try some DSO imaging with it as well. I have just ordered a celestron f6.3 reducer/corrector which i believe has a focal distance 105mm (back of reducer to camera chip). As i am using a Canon full frame camera with a back focus of approx 55mm, i was thinking of getting a M48x0.75 spacer made up which will sit between the reducer and the canon t mount. I figure that the effective length of the spacer should be 50mm. I think this sounds correct but before i order it, can anyone confirm that my calculation is correct?
With thanks
Spacing sounds correct, but why the M48 thread?
The rear of the reducer is the standard 2” SCT thread and the T thread adaptor for the camera is the standard 42mm T thread.
I had a Celestron Off Axis Guider lying around so I mated it with my Celestron x0.63 Reducer/Corrector and came up with the following measurements, based on the following assumptions:
Celestron designed their OAG to be used as follows:
Canon EF Mount: distance from the mounting Flange (the metal ring on the camera and the rear of the lens) to the Film Plane = 44mm.
T-mount requires a 55mm Flange to Film Plane distance, therefore T-Ring is 11mm thick.
The 1st attached file shows the Celestron Off Axis Guider mated with my Canon 5D and the Celestron x0.63 Reducer/Corrector (RC).
When the Celestron OAG is screwed into the Celestron RC, the distance between the T-Ring flange and the interface between the OAG Flange and RC Rear threaded Face is 50mm (inside the knurled ring of the OAG).
This gives an overall measurement of 44 + 11 + 50 = 105mm.
