title: Second-order imaging properties of circular field spectrographs.
abstract: The second-order focusing properties of a grating spectrograph with fixed entrance slit and a circular image field are investigated analytically. It is shown that the Rowland mount is the only circular field spectrograph mount which allows perfect tangential focusing (to second order) over a predetermined wavelength range, while two classes of mounts exist, one of which is nontrivial, for which astigmatism is corrected exactly on a circular arc.
authors.forename: C
authors.initials: C
authors.lastname: Palmer