Infrared Passbands for Precise Photometry of Variable Stars by Amateur and Professional Astronomers

Volume 36 number 1 (2008)

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Eugene F. Milone

Department of Physics and Astronomy, University of Calgary, 2500 University

Andrew T. Young

Astronomy Department, San Diego State University, PA-2105500 Campanile Drive,

Abstract

The infrared (IR) spectral region is a rich one for variable star work, especially of cooler stars, but it is hard to do IR photometry because of high, variable background, and specialized telescopic equipment that is usually required to obtain meaningful data. Typically, telescopes with IR detectors are at high elevations, to minimize water vapor absorption. Nearly all the filters produced for astronomical work at observatories around the world have not been optimized for use at anything other than the highest and driest of observatories. This has made it difficult for amateur astronomers to contribute to this field. Now, however, this is no longer the case. The IAU's Infrared Working Group (IRWG) has designed and tested a set of IR filters less sensitive to water vapor, permitting observations at any site where precise optical photometry can be carried out. Data acquired with these filters can be corrected easily for atmospheric (water vapor) extinction, unlike the situation with the older IR filters. We demonstrate this with data from the University of Calgary's Rothney Astrophysical Observatory.