Skywatcher arrived today, the MaxDSLR arrived yesterday. Couldnt wait to play with it. However, I found the MaxDSLR does not screw onto the eyepiece holder, I have a t ring which screws on ok. I tried the setup with this and was pleased that at 800 ISO and a target at over 25 meters shutter speeds can still be quite high and AF confim light works ok(had a widow of sunshine).
Measured this distance (with my sigma 150-500) and found minimum focus distance to be 25.1 meters with camera attached to scope with just a Tring.
I also have a Opticron push fit adapter with Tring thread so tried this, compression ring was too small for secure attachment but I held it on without, found a target that I could focus on at minimum distance and measured this, minimum distance was now at 11.2 meters.
I then measured the extra 'spacing' the push fit gave over just a Tring, this was about 22.5mm. I then calculated that for each mm spacing, minimum focus would be reduced by approximately .6 meters. So when those ext tubes arrive I could (in theory) get minimum focus distance of 7.1 meters with the 30mm tube.
Unless of course my theory is incorrect.
Also, a quick question: is this the correct formula tocalculate an eyepiece magnifictaion factor: