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 and his nebulous objects as yellow 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 reference stars as black crosses (the same star set as on these reference maps) at their positions 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.

The modern constellation boundaries precessed to Ptolemy's equinox are also represented: an anachronism for sure, but it helps situate things. The maps are framed around the modern constellation boundaries exactly like the reference maps. The comparison reveals the modern names of Ptolemy's stars, shows the effect of the precession of the equinoxes on the coordinate systems after almost two millennia (compare for instance the positions of the north pole on the Ursa Minor maps), and the displacement of high proper motion stars over this length of time (61 Cyg, μ Cas, α Cen, α Boo (Arcturus) are dramatic examples).

On the whole, the modern boundaries enclose their Ptolemy stars fairly well. Some of the modern constellations have annexed informes stars from Ptolemy's constellations. For instance,

  • Canes Venatici, Leo Minor, 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.

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.

The maps are enumerated in the same order as the constellations in Ptolemy's catalog. Larger constellations (Eridanus, Hydra, Argo Navis) and Serpens use more than one map. Maps covering Lynx, Coma Berenices, Columba, Monoceros, and Microscopium have been added even though they are not Ptolemaic constellations to ensure that every Ptolemy star is represented on at least one map.

Ursa Minor
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UMI
Ursa Major
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UMA
UMa (in Lynx)
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LYN
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
Leo (in Coma)
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COM
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 (N)
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ERI_N
Eridanus (S)
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ERI_S
Lepus
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LEP
Canis Major
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CMA
CMa (in Col)
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COL
CMa (in Mon)
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MON
Canis Minor
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CMI
Navis (Puppis)
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PUP
Navis (Vela)
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VEL
Navis (Carina)
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CAR
Hydra (East)
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HYA_E
Hydra (West)
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HYA_W
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
PsA (in Mic)
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MIC

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.