Abstract
Significant effort has been expended to locate and characterize small groups of stars for use as stable, well-known calibration sources. However, virtually all stars brighter than visual magnitude 16 have had their irradiance measured multiple times, with large or unknown error bars. Magnitudes in astronomical bands are gathered into several catalogs that provide good point source coverage of the entire sky, if the errors are acceptably small. SDL has been developing systems that use star radiometric data from catalogs and online sources to monitor atmospheric properties over large sky regions at night. The quality of the star catalog radiometric data is one of the main error sources in this work. This presentation shares what we have learned about quality and use of star catalog radiometric data with calibrated sensors. While data for many individual stars might be questionable, the combination of measurements from hundreds or thousands of stars can be surprisingly useful. We include data comparisons of catalog results to well-characterized reference UBVRI Landolt stars and other recent standards. The wider data sets are good enough to measure night atmospheric properties such as line-of-sight transmission (optical depth) over a useful range of values, using automated techniques.
Radiometric Quality and Usefulness of Star Catalog Data
Significant effort has been expended to locate and characterize small groups of stars for use as stable, well-known calibration sources. However, virtually all stars brighter than visual magnitude 16 have had their irradiance measured multiple times, with large or unknown error bars. Magnitudes in astronomical bands are gathered into several catalogs that provide good point source coverage of the entire sky, if the errors are acceptably small. SDL has been developing systems that use star radiometric data from catalogs and online sources to monitor atmospheric properties over large sky regions at night. The quality of the star catalog radiometric data is one of the main error sources in this work. This presentation shares what we have learned about quality and use of star catalog radiometric data with calibrated sensors. While data for many individual stars might be questionable, the combination of measurements from hundreds or thousands of stars can be surprisingly useful. We include data comparisons of catalog results to well-characterized reference UBVRI Landolt stars and other recent standards. The wider data sets are good enough to measure night atmospheric properties such as line-of-sight transmission (optical depth) over a useful range of values, using automated techniques.