Introduction

The surface density of bright QSOs (B < 17.0) is still very poorly known. The PG survey (Schmidt & Green 1983) covering an area of 10714 deg² lead to the discovery of 69 QSOs brighter than M_B = -24 ($H_{\rm o}$ = 50 kms^-1Mpc^-1) and B = 16.16, corresponding to 0.0064 deg^-2. However, several authors have concluded that it could be incomplete by a factor 2 to 3.

The First Byurakan Survey (FBS), also known as the Markarian survey, was carried out in 1965-80 by Markarian et al. (1989). It covers 17000 deg² and is complete to about B = 16.5$^{\rm m}$. It has been used by Markarian and his collaborators to search for UV excess galaxies; it can also be used for finding UV-excess starlike objects. Such a program -- the second part of the FBS -- has been undertaken in 1987 (Abrahamian et al. 1990; Mickaelian 1994). Its main purpose is to take advantage of the large sky area covered to get a reliable estimate of the surface density of bright QSOs.

At the present time, 4109 deg² have been searched and a catalogue of 1103 blue stellar objects (715 at $\vert b \vert \gt$ 30$^{\rm o}$) has been built. 434 spectroscopic identifications (398 stars and 36 QSOs) are already known. Photoelectric UBV photometry for 113 FBS objects has been published. For all except one, U - B < -0.50.