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DISCOVERY OF
HIPPARCHUS’ LOST
STAR CATALOG ON
THE FARNESE ATLAS
BRADLEY E. SCHAEFER
(Louisiana State University)
HIPPARCHUS Greatest Astronomer of Antiquity
Rhodes: fl. 140-125 BC
Only surviving work is his
Commentary
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First Star Catalog (~1000 stars)
Discovered Precession
First Nova
First Model for Solar & Lunar
Motion
• Best Planetary Observations to
Date
FARNESE ATLAS
SHOWS:
• 41 Constellations
(no stars)
• Equator, Tropics
• Colures
• Arctic, Antarctic
Circles
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POSSIBLE DATES FOR
OBSERVATIONS USED TO PLACE
THE CONSTELLATIONS
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c. 150 AD
c. 128 AD
c. 275 BC
c. 366 BC
1130±80 BC
Contemporary with Roman sculptor
From Ptolemy’s Almagest
From Aratus’ Phaenomena
From Eudoxus’ Phaenomena
Assyrian observer who was source for
Eudoxus and MUL.APIN
GET DATE FROM CONSTELLATION
POSITIONS
Constellations positions shift slowly with the centuries (due to
precession), so the depicted positions provide a ‘clock’
PRECESSION
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DATE OF FARNESE ATLAS
CONSTELLATION DATA
• New photographs taken in Naples last June
New photos required as camera-globe distance must be known for photogrammetry
• 70 constellation positions measured to 1.5° accuracy
• Chi-square fit to find the best date
 125 BC (±55 years)
 REJECTS Ptolemy, Aratus,

Eudoxus, and the Assyrian
MATCHES Hipparchus
DATE OF FARNESE ATLAS
CONSTELLATION DATA
• Accuracy of original data is <2°
• Ancient star catalogs have accuracy <1°
• Ancient verbal descriptions have accuracy >4°-8°
 Original data must be from a star catalog
 Only Hipparchus and Ptolemy
have old star catalogs
(and Ptolemy is too late)
DETAILED COMPARISON BETWEEN
ATLAS AND ANCIENT SOURCES
• Phaenomena of Aratus & Eudoxus
12 significant differences
e.g., solstice off by 35°!, Centaur not under Scorpion, Eridanus extends almost to Dog
• Commentaries of Hipparchus
0 differences
• Catasterismi of Pseudo-Eratosthenes & Eratosthenes
9 significant differences
e.g., Southern Crown is present, Hercules is kneeling, Pegasus has wings
• Almagest of Ptolemy
11 significant differences
e.g., Equuleus and Bernices’ Hair missing, Eridanus extends almost to Dog, Archer has no cloak
CONNECTING THE FARNESE ATLAS
TO HIPPARCHUS’ CATALOG
• 3.5° ACCURACY REQUIRES A STAR CATALOG
Only Hipparchus and Ptolemy have ancient star catalog
• FARNESE ATLAS POSITIONS FROM 125 ± 55 BC
Eliminates Ptolemy, Aratus, Eudoxus, the Assyrian, and any contemporary
Only Hipparchus is consistent with date
• CONSTELLATION ICONS MATCH HIPPARCHUS
Eliminates Ptolemy, Aratus, Eudoxus, and Eratosthenes
Only Hipparchus matches the Farnese Atlas
 FARNESE ATLAS BASED ON THE
LOST STAR CATALOG OF
HIPPARCHUS
APPLICATIONS
• WHAT COORDINATE SYSTEM DID HIPPARCHUS USE?
None? Equatorial? Ecliptic? Mixed?
EQUATOR, COLURES, TROPICS  EQUATORIAL COORDINATES
• HOW MUCH OF HIPPARCHUS’ CATALOG IS IN THE ALMAGEST?
None? Small fraction? Large fraction? All?
In past, we have only had partial positions for some stars (from the Commentary)
are known, and these have an unknown relation to the star catalog
NOW, WE HAVE HIPPARCHUS’ FULL CATALOG 
FUTURE WORKERS WILL TEST FARNESE ATLAS vs.
ALMAGEST
CONCLUSIONS
THE LOST STAR
CATALOG OF
HIPPARCHUS IS
DEPICTED ON THE
FARNESE ATLAS