Mike Jones wrote in message ...
Mike Jones wrote:

You will likely have to re-focus the CCD as you rotate the
grating, especially as you get into the ultraviolet where best focus is
rapidly moving toward the lens.


Sorry - caught myself after I hit SEND - your achromat will have a minimum
EFL somewhere in the green. The EFL will increase toward the red and blue,
and REALLY increase into the UV.

This is what I was thinking, that the change in EFL[wavelength] will
work in the opposite direction as the field curvature of the objective
canceling (e.g. flattening) some of it out.

Thanks

Mitch