The star maps below represent the stars of Ptolemy's catalog, one constellation at a time, along with the corresponding stars according to modern catalogs. As explained here, the available versions of Ptolemy's catalog offer different coordinates, magnitudes, and star associations for many stars. These maps follow Toomer's version, the most recent.

Following Verbunt & van Gent [1], I have assumed that the epoch of Hipparchus's observations is JD 1,674,573 (in the year 128 BCE) and the equinox of Ptolemy's coordinates JD 1,771,298 (in the year 137 CE). The maps represent stars in the ecliptic coordinate system corresponding to that equinox (the obliquity of the ecliptic, according to the IAU 2006 precession model, was at that time close to 23.68°).

The maps represent Ptolemy's stars as blue disks. Following [1] again, I have obtained their positions by substracting 2°40' from Ptolemy's longitudes to reduce them to Hipparchus's epoch, and precessed the result from Hipparchus's epoch to Ptolemy's equinox. The coordinates obtained this way differ from the original ones by 1° in longitude on average, compensating for Ptolemy's error (wrong precession value or flaw in his solar theory, as explained in [1]), and result in a much better match with modern positions.

The maps also represent the bright stars up to magnitude 6.25 as black circles. Their positions were taken from the Hipparcos catalog, brought back to Hipparchus's epoch according to their proper motion, and precessed to Ptolemy's equinox. Each Ptolemy star is linked by a straight line segment to its modern equivalent(s) according to the chosen version of Ptolemy's catalog.

Ptolemy stars are labeled with their number in their constellation. The label includes the constellation abbreviation when the star falls outside the boundaries of the corresponding modern constellation(s), drawn with a white background. I use a tilde (~) character before the number or between the constellation abbreviation and the number to denote informes stars. Reference stars linked to Ptolemy stars are labeled with their Bayer/Lacaille Greek or Latin letter if any, or Flamsteed number if any.

The modern constellation boundaries precessed to Ptolemy's equinox are also represented: an anachronism for sure, but it helps situate things. They look askew in the ecliptic coordinate system since they are based on equatorial coordinate lines (of the B1875.0 epoch). On the whole, the modern boundaries enclose their Ptolemy stars fairly well. Some of the ancient constellations have been modified, notably by Lacaille in the southern hemisphere. For instance,

  • the stars of Argo Navis belong to the modern Puppis, Carina, Vela, and Pyxis,
  • the modern Crux has been carved out of Centaurus.

Some of the modern constellations have annexed informes stars from Ptolemy's constellations. For instance,

  • Canes Venatici and Lynx contain informes stars from Ursa Major,
  • Coma Berenices has informes stars from Leo,
  • Columba has informes stars from Canis Major,
  • Microscopium has informes stars from Piscis Austrinus.

The maps are enumerated in the same order as the constellations in Ptolemy's catalog.

Ursa Minor
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UMI
Ursa Major
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UMA
Draco
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DRA
Cepheus
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CEP
Boötes
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BOO
Corona Borealis
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CRB
Hercules
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HER
Lyra
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LYR
Cygnus
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CYG
Cassiopeia
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CAS
Perseus
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PER
Auriga
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AUR
Ophiuchus
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OPH
Serpens Caput
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SER1
Serpens Cauda
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SER2
Sagitta
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SGE
Aquila
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AQL
Delphinus
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DEL
Equuleus
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EQU
Pegasus
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PEG
Andromeda
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AND
Triangulum
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TRI
Aries
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ARI
Taurus
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TAU
Gemini
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GEM
Cancer
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CNC
Leo
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LEO
Virgo
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VIR
Libra
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LIB
Scorpius
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SCO
Sagittarius
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SGR
Capricornus
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CAP
Aquarius
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AQR
Pisces
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PSC
Cetus
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CET
Orion
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ORI
Eridanus
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ERI
Lepus
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LEP
Canis Major
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CMA
Canis Minor
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CMI
Argo Navis
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NAV
Hydra
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HYA
Hydra (cont.)
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HYA_
Crater
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CRT
Corvus
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CRV
Centaurus
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CEN
Lupus
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LUP
Ara
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ARA
Corona Australis
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CRA
Piscis Austrinus
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PSA

References

[1] The star catalogues of Ptolemaios and Ulugh Beg by F. Verbunt and R. H. van Gent, Astronomy & Astrophysics, 455, A31 (2012).


Acknowledgments.

  • This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23.
  • This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.