Re: Transmission grating in a converging beam


Ken Harrison
 

Andrew,
Interesting result.
I used the Bowen and Vaughan reference, as well as the detailed analysis in Schroeder "Astronomical Optics", p297 to update the focus for the grating in a converging beam in the latest TransSpec spreadsheet..
Schroeder explains the s/3 by working from the Monk-Gillieson arrangement.
He focuses on the TTC to develop his chromatic coma equations and in the end recommends the camera should be tilted to give a "best fit the the curved field.
The resolution of the grating therefore seems to be limited by chromatic coma and out of focus conditions due to the field curvature.

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"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....

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