Download the free CCD calculator from
here , and you wont have to calculate anymore, its simple and usefull
.
If you undersample,(or even if you dont), doubling the image size in PS before you start processing I found gives less pixely stars and better results generally in the end (especially with the sharpen and deconvolute filters). Its sort of cheating, and guru math says its rubbish, but just through trial and error, it works. Although processing is of course slower.