THE SPACELAB-1 VERY WIDE-FIELD SURVEY OF UV-EXCESS OBJECTS .4. THE PERFORMANCE OF THE INSTRUMENT IN COMBINATION WITH OPTICAL PHOTOMETRY AS A MEANS OF IDENTIFYING STARS WITH PECULIAR PROPERTIES

UV (195 nm) and Stromgren uvby photometry of a 110 square degree field at high southern galactic latitudes are analyzed through a comparison of i) UV magnitudes for 57 stars of various types common to the publi shed TD1 catalogue and the Very Wide Field Camera (VWFC); and ii) obse rved and theoretical two-colour diagrams. The higher sensitivity of th e VWFC (similar or equal to 0.5 magnitude) and its more complete surve y are exemplified by the detection and UV measurement of a series of o bjects with moderate UV-excess in addition to detection of some very b lue objects of various nature down to fainter than 12th magnitude in t he optical domain. A deeper survey with a VWFC-type instrument could p rovide a complete sample for studies of the group properties of faint blue stars. During the uvby reductions it was found that the usual pro cedure of plotting residuals as functions of declination, hour angle a nd airmass can be a powerful and diagnostic test of photometer rigidit y.