Hi,
After a chat at last nights non-viewing evening I was asked to put some details up on the message board relating to how to make a focus aid for astrophotography. Firstly here's a link for a professional version: -
http://www.digitalastronomy.com/html/focus-master_telescope_focusin.asp
You will see all it comprises of is a black disk that goes over the end of the talescope with three holes at 120 degree angles, these professional versions are about £60+.
Or you can just use a bit of cardboard and save £60: -
http://www.newastro.com/newastro/book_new/c2_d.asp
Have fun, because they really work well.
very useful thanks alot