This paper, published in Baltic Astronomy Vol. 5 No. 2, pages 281--295, 1996, contains the following errors: p. 281 in the title: should be PHOTOMETRY; p. 282 in Eq. (2) should be e(-h/7.996) ; p. 283 in lines 5--6 from the bottom should be: of the altitude of a ground-based observatory; p. 284 in line 8 from the bottom should be: alpha = nu (*) - 2; p. 287 in Table 1: the units for the extinctions are mags/airmass and for the ozone absorption is cm(-1) . After the author proofs were received, these errors were corrected in a part of copies of the journal.