AAVSO: American Association of Variable Star Observers

Simplifed Color Photometry Using APASS Data (Abstract)

Volume 42 number 2 (2014)

Nicholas Dunckel
12971 Cortez Lane, Los Altos Hills, CA 94022; ndunckel@earthlink.net


(Abstract only) APASS, the AAVSO Photometric All-Sky Survey, now contains 47 million stars and covers 97% of the Northern and Southern hemisphere sky. Its extraordinary coverage means that there are multiple APASS-calibrated stars available for color photometry in the field of view of virtually every amateur image. This paper presents a simplified spreadsheet-based procedure that combines raw photometric data with APASS data to calibrate target objects in the same field of view. The complete photometric equations are reviewed and a simplified form is obtained for use within a limited field of view. Raw photometric data and APASS data for that image from AAVSO are combined on a spreadsheet to produce calibrated photometric measurements of target objects within the field of view. The consistency of the fit to the data is shown graphically. Error terms are tracked through the equations to provide the standard deviation of each measurement.