J/other/JHA/47.294 Ilkhanid star table (1232) (Mozaffari, 2016)
A medieval bright star table: the non-Ptolemaic star table in the Ilkhani Zij.
Mozaffari S.M.
<Journal for the History of Astronomy, 47, 294-316 (2016)>
=2016JHA....47..294M 2016JHA....47..294M (SIMBAD/NED BibCode)
ADC_Keywords: Historical catalog ; Positional data
Keywords: Maragha observatory - Ilkhani zij - Islamic astronomy -
medieval astronomy - star table - Ptolemy - Almagest
Abstract:
The Ilkhani zij compiled by Nasir al-Din al-Tusi and his colleagues in
the first period of the astronomical activities (the 1260s and early
1270s) in the Maragha observatory includes a star table collecting
important observations of Islamic astronomers from the early ninth
century through the third quarter of the thirteenth century, including
the Mumtahan astronomers, Ibn al-A'lam, Ibn Yunus, as well as the
Maragha astronomers themselves. This table gives the ecliptical
coordinates of 18 bright stars in comparison with Ptolemy's
corresponding values. This medieval bright star table is especially
interesting for two reasons: first, it provides reliable evidence for
the examination of the accuracy of the observations made and the
instruments employed (notably, an armillary sphere) in the Maragha
observatory. Second, it facilitates a comparative study of the
accuracy of stellar observations in medieval Middle Eastern astronomy
in the period in question. We have obtained the result that the
Maragha astronomers observed more accurate star longitudes than did
their predecessors, while for the latitudes, all Islamic observers
appear to have gained about the same degree of accuracy. We also
discuss two delicate matters raised by this table: first, the problem
of the use of the two different values for the rate of precession by
the Maragha astronomers in order to convert earlier star longitudes to
the epoch of the Ilkhani zij (1°/66 years for Ptolemy's
longitudes and 1°/70 years for those measured by their Islamic
predecessors); second, the change in the star latitudes essentially
related to the various values measured by Ptolemy and the Islamic
astronomers represented side-by-side in it. Finally, we briefly
discuss a small celestial globe designed by the son of Mu'ayyad
al-Din al-'Urdi, the instrument-maker of the Maragha observatory.
Description:
We present machine-readable version of the bright star table of
the Ilkhanid astronomical table (1232). It contains the ecliptic
coordinates of the 16 stars from this historical table, their modern
identification with Bayer designation, and the modern coordinates
computed on the basis of the Bright Star Catalogue for the time.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
margha01.dat 38 16 The Ilkhani bright star table
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See also:
V/61 : Almagest (Ptolemy's Star Catalog)
J/A+A/516/A28 : Star catalogue of Tycho Brahe (1627) (Verbunt+, 2010)
J/A+A/516/A29 : Star catalogue of Hevelius (1690) (Verbunt+, 2010)
J/A+A/530/A93 : de Houtman, Kepler and Halley star catalogs (Verbunt+ 2011)
J/A+A/544/A31 : Star catalogues of Ptolemaios, Ulugh Beg (Verbunt+, 2012)
Byte-by-byte Description of file: margha01.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- IZ [1/16] Sequence number in the non-Ptolemaic
star table in the Ilkhani zij
4- 10 A7 --- Name Bayer designation and abbreviation of
constellation name
12- 14 I3 deg Elono.d [0/360] Degrees of the ecliptic longitude as
given in the non-Ptolemaic star table in the
Ilkhani zij (1)
16- 17 I2 arcmin Elono.m [0/59] Minutes of the ecliptic longitude as
given in the non-Ptolemaic star table in the
Ilkhani zij (1)
19 A1 --- Elato.- [±] Sign of ecliptic latitude as latitude
as given in the non-Ptolemaic star table in
the Ilkhani zij (1)
20- 21 I2 deg Elato.d [0/90] Degrees of the ecliptic latitude as
given in the non-Ptolemaic star table in the
Ilkhani zij (1)
23- 24 I2 arcmin Elato.m [0/59] Minutes of the ecliptic longitude as
given in the non-Ptolemaic star table in the
Ilkhani zij (1)
26- 28 I3 deg Elon.d [0/360] Degrees of the ecliptic longitude as
computed from the bright star catalogue for
18 January 1232 AD
30- 31 I2 arcmin Elon.m [0/59] Minutes of the ecliptic longitude as
computed from the bright star catalogue for
18 January 1232 AD
33 A1 --- Elat.- [±] Sign of ecliptic latitude as
computed from the bright star catalogue for
18 January 1232 AD
34- 35 I2 deg Elat.d [0/90] Degrees of the ecliptic latitude as
computed from the bright star catalogue for
18 January 1232 AD
37- 38 I2 arcmin Elat.m [0/59] Minutes of the ecliptic latitude as
computed from the bright star catalogue for
18 January 1232 AD
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Note (1): The variants given for the ecliptic coordinates in the preserved
manuscripts of the Ilkhani zij are presented on page 298 of
the paper.
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Acknowledgements:
S. Mohammad Mozaffari, mozaffari(at)riaam.ac.ir
(End) S.M. Mozaffari [RIAAM, IRAN], Patricia Vannier [CDS] 09-Nov-2017