[Galah (Patrick)]

Any number of references I have seen seem to equally state that there is / is not field curvature. Can anyone you provide some definitive data / reality re the Intes MN-66?

I am now turning to the long-planned investigation of spectroscopy. The device of initial interest is the LHIRES III. One concern is the amount of back-focus that might be required - is anyone able to advise where-is or how to find the focal point in my system - MN-66 (152mm F/6 with a JMI NGF DX1 fitted).
The JMI info. is in the attached .doc file.