Field correctors for a one-meter, f/15 cassegrainian telescope were designed as part of a NASA-funded study of an astronomical obervatory on board of the Space Shuttle. By means of a Gasgoigne corrector and a biconcave field flattener, astigmatism and field curvature are corrected in a 0.6 deg field. Applicable wavelength ranges are limited by chromatic aberrations. The upper wavelength is selected to match a photocathode response limit. The lower wavelength limit is defined by a filter. Examples of usable wavelength ranges are: 210 nm - 1100 nm (multialkali photocathode, fused-silica corrector elements), 177 nm - 320 nm (cesium telluride photocathode, calcium fluoride correctors); and possibly 134 nm - 190 nm (cesium iodide photocathode, lithium fluoride correctors). Residual rms lateral color is smaller than 0.02 arc sec, and axial color is smaller than 0.25 arc sec (blur diameter at the ends of the wavelength range). The correctors introduce a small amount of coma. This is compensated by adjustment of the conic constants of the telescope mirrors.

Refractive Field Correctors For The Starlab Ultraviolet Telescope

Parameters are given for a corrector lens design which will provide a 0.5 degree field of good definition from 134nm to 280nm at the Ritchey-Chretien focus of the F/2-F/15 Starlab 1-metre telescope. The optimization includes the window of the detector which is aspherized on the outside but not on the inside where the photocathode is deposited. The 130 mm diameter detector is preceded by two lenses, the first of which is convex-plano. Because this element has a flat surface it can be interchanged with other elements to either compensate for the chromatic aberration of filters (by making the lens thinner), and/or to provide dispersion for multi-object slitless spectroscopy. In the latter case, the interchanged element is wedged and has a course transmission grating deposited on the flat side. This combination of grating and lens is referred to as a grens.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Harvey Richardson

Papers

Field Corrector Lens And Grens For The Starlab Ultraviolet Telescope. I. Photocathode On Window