Satgen 641  Name that Star  by GM4IHJ  (BID SGEN641)    2001-07-07

A few days ago, a friend asked for guidance in finding Comet Linear
C/2001 2A, which is now showing in the predawn south eastern sky of
the Northern Hemisphere. If that is unlike IHJ, you live far enough
south to get a night sky at this time of year.

The track chart for the comet featured its path through the
constellation of Pisces, below the constellation of Pegasus. With the
best located nearby marker star, anywhere near the viewing field,
being HAMAL.

Why Hamal ? Did'nt the Greeks invent astronomy in 300BC and name the
stars? Well no they did not . The Egyptians and the people of the Two
Rivers ( Tigris and Euphrates) were the first to describe and name
some of the stars. But the first practical users of astronomy for
anything other than calculating the dates of religious festivals and
events like the onset of the annual Nile flood, seem to have been the
Arabs. Long before European seamen began to explore across the
Atlantic , and down the west coast of Africa in the 15th century,
Arab seamen were making the long voyage down the Persian Gulf and
across the Arabian Sea to East Africa, and to do this safely they
needed stellar navigation.

Begining in 622 , with the emigration of the Prophet from Mecca to
Medina, there was a period of turbulence as Arab influence was
extended out of Arabia. By the 9th century however the establishment
of the Caliphate in Bagdad, brought a stable situation in which
science could flourish. Initially the Greek texts of Archimedes and
Ptolemy were translated into Arabic, and then gradually a wealth of
new material appeared including the whole compass of Arab/Indian
numerology and arithmetical procedures. Such that by 1100 AD an
Englishman studying in the then Arab province of Spain was able to
acquire fluency with Arab numbers . A great improvement on the
cumbersome Roman numerals then in vogue in Europe.

A great deal of this drive to improve mathematics lay in the need to
accurately calculate the dates of religious festivals. But the Arabs
were also practical seamen. So it is really no surprise that about
this time the six modern trigonometrical functions we now use every
day in our satellite orbital calculations , are first heard ,
together with the Arab names for the fixed stars.

The motions of the stars had long been tracked using the Astrolabe, a
two dimensional model of the sky engraved on rotatable brass plates.
But by the 12th century some beautifully engraved and accurate Arab
astrolabes had appeared . Including one which got to Merton College
in  Oxford England, complete with Arab names very close to the ones
we use today . Eg Alferaz, Algeuze, Altahir, Mirac, Rigil and Wega.

Today most navigation stars have either the indigenous Arab names or
, Arab translations of the Greek names used in Ptolemys catalogue.
All of which complements the fact that we are now begining to see
both commercial and amateur Arab satellites in our skies.