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CCD Photometry of SN 1974G from Photographic Plates Using a Kodak DCS200 Camera

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Valorie Burkholder

Maria Mitchell Observatory

Nantucket, MA 02554

Presented at the Annual Meeting of theAAVSO, October 15, 1994

Abstract

We have investigated the use of a Kodak DCS200 camera, which mounts a 1524 x 1012-pixel uncooled CCD as the detector in a conventional Nikon 8008s camera, to digitize and obtain photographic photometry from typical plates in the Maria Mitchell Observatory (MMO) plate collection. We tested the photographic stability of the camera system on photographic standard sequences in several fields, finding a linear correlation between instrumental aperture magnitudes and standard photographic magnitudes, with an rms deviation of 0.1 magnitude. We then applied the methods to digitize a 1 cm square area surrounding SN 1974G in NGC 4414 on a series of five plates taken within a week of maximum light. The major source of the 0.2magnitude uncertainty in SN 1974G magnitude measurements was determining the local background surrounding SN 1974G. However, the photographic magnitudes we derived agree within 0.2 magnitude of points interpolated from published light curves. We conclude that the Kodak DCS 200 camera is an excellent and economical device for digitizing small areas of plate collections for special study.