All-Moscow Seminar of Astrophysicists
(ASA)
The seminar is supported by the grant of Federal Programm "Integration"
annotation of talk
Zakharov, A.I. Mironov, A.V. (SAI)
"The Ancient Astrophotometry --- The time of "The Almagest" starcatalogue
creating from magnitudes of south stars."
Star altitudes at upper culmination
depends on the latitude and on the
precession period phase. That
altitudes can be easily calculated
for any epoch. The brightness of
stars with upper culmination
zenith distance more then 70
degrees are considerably extinct
by the Earth atmosphere.
By comparing the extincted southern
star magnitudes given in "Almagest"
with those obtained by modern
extra-atmosphere data reduced
to their location at different
epoches, one can estimate the
time and latitude of the Almagest
observation. The adopted extinction
coefficient of 0.25 mag leads to
the conclusion that the catalogue
data has been obtained at the middle
of 2-nd century b.c. at the latitude
of +31 deg. Besides it is quite
impossible for the catalogue
to be worked out at more northern
latitudes or to the south of
+ 26 deg. nor later than 2-nd
century b.c.