title: Wadsworth mount redux: paraboloidal versus spherical gratings.
abstract: Spherical and paraboloidal diffraction gratings are considered for use on an experiment involving a collection of satelliteborne spectrographs that will investigate astrophysical plasmas in the spectral region from approximately 100 to 300 A. We shall use eight spectrographs: Wadsworth mounts in near-normal incidence with effective focal lengths of 3 m, each centered on a chosen wavelength in this spectral range. Ray tracings show that paraboloidal gratings used in the Wadsworth mount have a significant increase in resolution over spherical gratings of the same effective focal length, used in the same mounting, as long as the spectral ranges are small (approximately 10% of the central wavelength). This increase in resolution is due to the spatial extent of coma for a paraboloidal grating that is less than the circle of least confusion of spherical gratings.
authors.affiliation: SFA, Incorporated, Woodlands Office Center, 9315 Largo Drive West, Suite 200, Largo, Maryland 20774, USA. wrhunter@bellatlantic.net
authors.forename: William R
authors.initials: WR
authors.lastname: Hunter
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kowalski
authors.forename: Raymond G
authors.initials: RG
authors.lastname: Cruddace