|
Description
Six Tautenburg 2-m Schmidt telescope plates have been used to derive proper motions for 12740 stars down to Blim=18.5 in the region centered at RA=83.45grad, Dec=-5.20grad of the Great Nebula in Orion. Each plate covers a 3x3 grad region of sky, with a scale of 51.4"/mm. The largest difference between the epochs is 36 years. The photographic plates were scanned using Tautenburg Observatory plate scanner. The accuracy of the scans was 0.5micron, and the scale was 1000pixels/mm. The rectangular coordinates x, y and instrumental magnitudes were then determined using a dedicated software. To convert the scanned positions to the equatorial coordinates we adopt reference stars from the ACT catalog. Mean errors of position determinations are 3-4mas. The components of the proper motions and their rms uncertainties were obtained via linear least-squares fit to individual rectangular coordinates as a function of the observing epoch with no less than three epochs for every proper motion. The mean measurement uncertainty is 3.5mas/yr in magnitude interval 15-19 and 5.0mas/yr outside this interval. The photometry has been taken from Walker (1969) for B-magnitudes, and from USNO-A2.0 for R-magnitudes. Mean errors for photometry are 0.03mag in B and 0.25mag in R. The ORICAT is supplemented with the data of Parenago (1954) (stars with numbers greater 17000), and includes 13 577 stars in total. ACKNOWLEDGMENTS. We thank E. Schilbach, N.V. Kharchenko, and R.D. Scholz for numerous discussions of the results, and J. Brunzendorf and H. Meusinger for help in organizing the work at Jena Observatory.
|
