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Photographic photometry with Iris diaphragm photometersA general method is presented for solving problems encountered in the analysis of Iris diaphragm photometer (IDP) data. The method is used to derive the general shape of the calibration curve, allowing both a more accurate fit to the IDP data for comparison stars and extrapolation to magnitude ranges for which no comparison stars are measured. The profile of starlight incident and the characteristic curve of the plate are both assumed and then used to derive the profile of the star image. An IDP reading is then determined for each star image. A procedure for correcting the effects of a nonconstant background fog level on the plate is also demonstrated. Additional applications of the method are made in the appendix to determine the relation between the radius of a photographic star image and the star's magnitude, and to predict the IDP reading of the 'point of optimum density'.
Document ID
19810051558
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Schaefer, B. E. (MIT Cambridge, Mass., United States)
Date Acquired
August 11, 2013
Publication Date
May 1, 1981
Publication Information
Publication: Astronomical Society of the Pacific
Subject Category
INSTRUMENTATION AND PHOTOGRAPHY
Funding Number(s)
CONTRACT_GRANT: NAS8-27972
Distribution Limits
Public
Copyright
Other