UBV stellar photometry of bright stars in GC M5 – I. UV colour–magnitude and colour–colour diagrams and some peculiarities in the HB stellar distribution
1Institute of Astronomy, Bulgarian Academy of Science, National Astronomy Observatory Rozhen, PO Box 136, BG-4700 Smolyan, Bulgaria;2Institute of Astronomy, Bulgarian Academy of Science, 72 Tsarigradsko ch., BG-1784, Sofia, Bulgaria