The Hamburg Quasar Survey. I. Schmidt observations and plate digitization.
HAGEN H.-J., GROOTE D., ENGELS D. and REIMERS D.
Abstract (from CDS):
The Hamburg Quasar Survey is a wide-angle objective prism survey for finding bright QSOs in the northern sky. It currently intends to provide a complete sample of bright, high-redshift QSOs in an area of ∼14000deg2, and to provide the base for an efficient identification of ROSAT AGNs. In this paper we describe observational techniques used in obtaining the Schmidt plate exposures and a fast digitization technique, developed to make surveys for finding AGNs in large areas of the sky. Digitization of a 24x24cm2 direct plate is achieved in 9 hours, while objective prism plates are scanned in less than three hours with decreased resolution.. Until the end of 1993 1199 Schmidt plates in 451 fields (∼11000deg2) had been taken and their digitization is now completed. Tests of the performance of the digitization technique show that reliable detection of the spectra is obtained to density levels 0.25-0.4 above background. This is sufficient for searches of complete samples of objects with 13≲B≲17.5 on digitized objective prism plates.
methods: data analysis - techniques: spectroscopic - surveys - quasars: general