increasing number of space particles, since about 30 particles on the average are registered during a 10 minutes’ exposure. A total of $\approx 5.7$ hours of open shutter time was eventually obtained for the observation of the GRB790613 error box. Atmospheric conditions were stable throughout the observational runs with a seeing of $1.1 - 1.7$ arcseconds. The first observation of this box was carried out on 13/14 April, 1994 in the [*B*]{} and [*V*]{} filters (Sokolov et al., 1994), where blue “candidates” were selected by the criterion $B-V < 0$. An additional observation in [*R*]{} filter was made on 2/3 June, 1994, but the CCD was not in the standard mode, and we used these data only as a photometric reference of relatively bright stars in the [*R*]{} filter over the whole mosaic obtained later. A subsequent observation in the three ([*BVR*]{}) filters of the central part of the GRB790613 error box, where several blue ($B - V < 0$) objects were found, was carried out on 29/30 December, 1994, and for the whole field — on 24/25 April, 1995.

The coordinates of the center of the studied field are $\alpha  (1950)
= 14^{h}12^{m}12^{s}.8;$ $\delta (1950) = +78^{o}54'13\farcs 8$. Unlike 