[Merlin66 (Ken)]

Can't do much else at the moment, so I made up a spreadsheet for the dispersion, resolution and spectrum size for a transmission grating (no slit) in a converging beam i.e. infront of a CCD in a telescope!
It allows you to enter telescope aperture, focal ratio, CCD details and distance to CCD chip and gives you an output.
You can then check if the full zero and spectrum will fit across your CCD chip, and by varying the parameters see the effect of varying the focal ratio and/or the distance to the CCD.
Give it a go. I'd obviously appreciate feedback.
I'll also post on the Astronomical Spectroscopy group.
ps Also "redone" Buil's Simspec to accommodate slits etc.