Photometry of Variable Stars Using a Lensless Schmidt Camera (Poster abstract)

Volume 37 number 2 (2009)

Jeff Horne

Abstract

(Abstract only) This paper describes the design and use of a lensless Schmidt camera (LSC) as a more cost effective alternative to more expensive telescope types. The lensless Schmidt design uses a short focal length spherical primary mirror and an aperture stop placed at the radius of curvature of that mirror. This results in an optical system without coma or astigmatism and a wide field of view. However, the LSC does have residual spherical aberration which enlarges the size of the stars being imaged by a CCD. The amount of spherical aberration tolerable in measuring stellar magnitudes and the physical length of the camera determine the possible focal ratio and aperture combinations for LSC designs. An LSC was built by the author and used to obtain data on several variable stars. Photometric V data plots for V Boo, χ Cyg, and U Cyg are provided as examples of the data than can be captured with this type of instrument.