Quote:
Originally Posted by OzEclipse
Hi Chris,
If the image you posted is an uncropped APS C, then the defocussed star diameter is about 15.7mm depending upon the specifics of your APS C sensor and blurring at the edges. If the FSQ 85 is the model with the 450mm focal length, then without any reducer this is a simple geometric similar triangles calculation:-
Extension required is approximately
15.5mm x 450mm = ~82mm
........85mm
I would retake the image with the Estatto at mid-travel rather than at one end measure the out of focus image and repeat the calculation.
Cheers
Joe
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Hi Joe,
That’s quite cool and not far off in agreement with the previous reply that appeared to have a 65mm and 25mm extension.
The only slight problem is I tried with and without the flattener and now I can’t remember whether that screen snip of Acrux was with or without! I’ll have to re-do it.