desperate help with astrophotography focusing !

[glowjet]

Cal, the calculations for your 900mm scope would suggest 3mm wide black strip in the form of a Y, the Y arms to be 20 degs or 40 degs apart, black plastic document cover is a popular material. fix this across the aperture of your scope, it does not have to be dead center, anywhere in the vicinity will be OK, if the resulting diffraction pattern is a little faint then widen the arms of the Y a little HTH

John.

[Paxo]

paxo, your images are amazing, how long have you been doing astrophotography? i can only hope to achive something even close to them

Thankyou. About three years, started with a DSLR then moved onto ccd's.

Steve

[cal1985]

thank you all for all your comments, this has been a great help and i will endevour to keep you all posted with any images i get that have been helped by you all. many thanks again