PHOTOGRAPHIC PHOTOMETRY FOR STELLAR STATISTICS WITH THE TAUTENBURG SCHMIDT TELESCOPE

Photometric properties of deep Tautenburg Schmidt plates in the UBV sy stem over the whole field and over a wide range of stellar magnitudes are discussed. Different reduction models based on the calibration cur ve alone and with additional terms containing colour and plate coordin ates are considered. With the filter-emulsion combination used the Joh nson UBV system can be reproduced quite well by the Tautenburg telesco pe. The accuracy of photometric data can be improved if geometrical te rms are taken into account. For deep plates with a significant effect of background nebulosity a supplementary term is to be included in the reduction model. The polynomial coefficients vary in dependence on sp ectral bands and individual properties of each plate.