Pauwels, T.

published in Virtual Observatory: Plate Content Digitization, Archive Mining and Image Sequence Processing, pp. 275-284 (2006)

Abstract: In this paper we present a tool to identify astronomical plates or CCD frames of which the right ascension, declination and scale are unknown. CCD pixels need not be square. At input a list of (x, y)-coordinates of stars should be supplied to the programme together with a 'magnitude' of the star. This magnitude need not be accurate, but is only used to determine which star is brighter than which other star. The programme then finds configurations of stars and tries to identify them in a data base of stellar configurations. Usually, most of these configurations will not be found, because e.g. a star in the catalogue may be listed as brighter than another one, while on the plate or frame, using another photometric system, it may be fainter. Other configurations may get a wrong identification, because somewhere else in the sky there is a similar configuration. However, 3 or 4 correct identifications, which then cluster in a small region in the sky, are enough to identify some stars and find the exact right ascension and declination of the centre of the plate. As a minimum the plate should cover about 10 x 10 square arcminutes and contain a few tens of GSC stars for the programme to work.

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