This paper deals with the brightness Changes of comet P/Halley in the
past. On the basis of the analysis of Sun-Earth-comet configuration at
the time of perihelion passage within 30 apparitions of the comet, si
nce 240 BC, several groups of apparitions of similar observing geometr
y were specified. These groups were analysed with emphasis on brightne
ss variations of the comet on different, long time scales. Absolute ma
gnitudes and duration of naked-eye visibility both in pre-perihelion a
nd post-perihelion periods of the comet are the main criteria for the
aim of in this study. Some brightness increase of the comet in 912-122
2 is indicated.