How to calculate whether rthe camera will focus

[keybaud]

I am going to get a MN190 for astrophotography and will be using a Canon DSLR with an OAG until I get a 'proper' camera. I am a complete novice and would be grateful if someone could let me know what I need to measure to ensure that the camera will be able to focus or point me to an article that explains what I need to do.

[Merlin66]

The DSLR needs 55mm space, add this to the length of your OAG body (say 40mm?) = 95mm

Point the scope at the moon and position a card 95-100mm behind the rear cell adaptor ring of the scope and see if you can bring an image of the moon into focus on the card using the scope's focusing knob.

I'd hazard a guess and say it will work OK.

[Pete Presland]

The DSLR needs 55mm space, add this to the length of your OAG body (say 40mm?) = 95mm

Point the scope at the moon and position a card 95-100mm behind the rear cell adaptor ring of the scope and see if you can bring an image of the moon into focus on the card using the scope's focusing knob.

I'd hazard a guess and say it will work OK.

what an excellent technique! i have never thought of that.