obtained at twilight along with bias frames at the end of each night of observation. By shifts and turns all images were reduced to a unified internal frame of reference. Cosmic particles were selected by subtraction of median smoothing over several images from one image and were removed individually. The whole processing was carried out with the use of the ESO-MIDAS software package.

[cccc]{}\
Number & B & V & R\
of area (Fig.2)& & &\
1,7 & 24.7 & 24.7 & —\
2.,3,5,6 & 25.7 & 25.7 & 25.6\
4 & 26.2 & 25.8 & 25.6\

The photometric standard star MS 1443+63 B was observed every observational night before and after observation of the GRB790613 error box. We used the star MS 1443+63 B to calibrate secondary standard stars inside the CCD mosaic. We used seven secondary standard stars for calibration of different frames for one night and for different nights. The total number of the objects registered up to 27$^m$ in the [*B*]{} filter is 426.

Photometry
----------

The images obtained and reduced to a unified frame of reference were summed up in each filter. Photometry was obtained for all objects inside the whole CCD mosaic. But for 