I got some good results with a 210mm f/4 camera lens and the free 66ED mask template from Focus-Mask which was sized just right. Here's a shot of Venus with it from tonight:
Taken at ISO200, 2sec, f/4. The mask didn't work at shorter FLs but I'm going to make a thinner one and see what happens.
-------------------- - Gill C. - Celestron Cometron CO-100, 10x25, 20x80, Binochair, Nikon D40
The Night Sky Atlas: www.nightskyatlas.com