Abr ar-Rahman Al Sufi (903-986 AD)
Abr ar-Rahman Al Sufi (or As Sufi) was living at the court of the
Emire Adud ad-Daula in Isfahan (Persia), and working on astronomical studies
based on Greek work, especially the Almagest of
Ptolemy.
He contributed several corrections to Ptolemy's star list, in particular he
did own brightness/magnitude estimates which frequently deviated from those
in Ptolemy's work.
Also, he was the first to attempt to relate the Greek with the traditional
arabic star names and constellations, which was difficult as these
constellations were completely unrelated and overlapped in a complcated way.
Al Sufi published his famous "Book of Fixed Stars" in 964, describing
much of his work, both in textual descriptions and pictures.
In his descriptions and pictures of Andromeda, he included "A Little Cloud"
which is apparently the Andromeda Galaxy M31.
He mentions it as lying before the mouth of a Big Fish, an Arabic
constellation. This "cloud" was apparently commonly known to the Isfahan
astronomers, very probably before 905 AD.
In this book, he probably also cataloged
the Omicron Velorum cluster IC 2391 as a
"nebulous star", and an additional "nebulous object" in Vulpecula, a cluster
or asterism now known as Al Sufi's or Brocchi's
Cluster, or Collinder 399.
Al Sufi image, NGC/IC observers page
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