Ijust used the freeware version of the CCD calculator from new astronomy.
http://www.newastro.com/newastro/dow...cdCalcFree.htm
You can put in the values for whatever equipment you have/want and let it do the calculations. If your camera isn't listed you may have to enter some data Eg chip dimensions and max resolution to get the pixel sizes, but its not to difficult. The freeware version has 3 images you can use to compare imaging areas of various setups.
It certainly makes it easy to quickly compare several different setups/combos.
Cheers,
John