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Description
This file, originally prepared for the needs of the Lowell Observatory Near-Earth Object Search (LONEOS), contains a rough working collection of Johnson-Cousins UBVRI photometry assembled mainly from the published literature or from publicly available datasets. The V-R and V-I colors are all on the Cousins system. Most of the stars are fainter than V=10.0; the median magnitude is V=13.9, and significant numbers of stars are listed below 20mag. Besides several large surveys, several hundred small sequences in the regions of variable stars, star clusters, galaxies hosting supernovae, quasars, etc were built by determining coordinates for the sequence stars using the published finder charts. At minimum the data include V magnitudes and at least one ordinary photometric color, most commonly B-V. The data were collected for use in determining approximate photometric zero-points in wide-field imaging, with external accuracy of 0.05 mag or better. Though each dataset was vetted for consistency in magnitude and colors, neither high accuracy nor high precision is guaranteed. Obvious variable stars were omitted, but some unknown variables are inevitably included. In any given field, it is advisable use all the available stars for calibration rather than a single comparison. Several large datasets are included. The Guide Star Photometric Catalogue (GSPC, Lasker et al 1988, Cat. II/143) provides BV sequences near the centers of all the Schmidt sky survey plates. At high latitudes in the southern sky, additional data on the 5-degree Schmidt grid were obtained by Platais et al (1998, Cat. I/277) that extend the GSPC sequences to V=~16. More southern fields were observed by Demers et al (1993A&AS...99..437D and 1993A&AS...99..461D); coordinates for these stars have been determined for the first time. Nearly a thousand high-quality sequences in the northern sky have been observed by Henden, partly published in relation to work on cataclysmic variables (e.g. Cat. J/PASP/107/324) and symbiotic stars (e.g. Cat. J/A+A/143/343). Additional Henden sequences have been adopted from the files cited below at the AAVSO ftp site. These large sequences were trimmed to include only a few stars per magnitude interval, and also to omit crowded stars (no significant companions closer than 15" radius). The star coordinates are mainly from early versions of the GSC or USNO series. As such they are given to 1" precision, and in some cases small systematic errors and (now) proper motion mean their accuracy is in the 1" to 5" range. Thus for automated linkage to CCD frames, some modest search radius should be adopted to match with the catalogue. Because the file was originally intended for private use, bibliographic references were not included except in a very few instances. Usually it is straightforward to recover the source paper by inspection of the SIMBAD bibliography for specific objects. Problematic cases can be directed to the compiler (Brian Skiff).
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