Dodwell's Data Table
| DATE | OBSERVATION | OBLIQUITY |
|
| B.C. 2045 | Karnak | 25° 09' 55" | summer solstice, sunset orientation |
| B.C. 1570 | Karnak | 24° 32' 06" | summer solstice, sunset orientation |
| B.C. 1100 | ancient Chinese | 24° 13' 56" | ancient observation, derived from "Chou-Pei" |
| B.C. 1100 | ancient Chinese | 23° 54' 04" | ascribed to Chou Kung, but corresponds to later date |
| B.C. 900 | ancient Hindu | 24° 11' 04" | derived from Jaina Astronomical Treatise "Suryaprajnapti" |
| B.C. 700 | ancient Chinese | 24° 02' 06" | derived from "Chou-Pei" |
| B.C. 700 | ancient Chinese | 24° 01' 50" | derived from "Chou-Pei" |
| MEAN | 24° 01' 58" | ||
| B.C. 558 | Thales | 24° 00' 56" | observations at Miletus |
| B.C. 510 | ancient Hindu | 24° 00' 44" | derived from the "Suryasiddhanta" |
| B.C. 326 | Pytheas | 23° 53' 46" | observations at Marseilles |
| B.C. 326 | Pytheas | 23° 54' 53" | observations at Marseilles |
| MEAN | 23° 54' 20" | ||
| B.C. 230 | Eratosthenes | 23° 52' 04" | observations at Alexandria |
| B.C. 230 | Eratosthenes | 23° 51' 47" | observations at Syene at Summer Soltice |
| B.C. 230 | Eratosthenes | 23° 51' 59" | observations at Syene at both Soltices |
| B.C. 230 | Eratosthenes | 23° 52' 12" | observations of shadowless area at Summer Solstice |
| MEAN | 23° 52' 00" | ||
| B.C. 135 | Hipparchus | 23° 52' 16" | observations at Rhodes |
| B.C. 130 | ancient Chinese | 23° 54' 04" | from figures given by Haui-Nan-Tzu (died B.C. 122) |
| B.C. 80 | ancient Chinese | 23° 53' 46" | observations at Loyang. Figures given by Lieou Hiang |
| A.D. 80 | Chinese | 23° 54' 04" | from figures given by the authors of the See-fen Astronomy, but result corresponds to earlier date of observation |
| A.D. 139 | Ptolemy | 23° 48' 16" | observations at Alexandria |
| A.D. 521 | Chinese | 23° 40' 36" | observations at Nanking (9 foot gnomon) |
| A.D. 521 | Chinese | 23° 41' 59" | observations at Nanking (8 foot gnomon) |
| A.D. 521 | Chinese | 23° 41' 31" | observations by Ouey Tartars at Kaifeng-fu, probably |
| MEAN | 23° 41' 22" | ||
| A.D. 578 | Chinese | 23° 41' 12" | observations at Sianfu |
| A.D. 579 | Chinese | 23° 41' 12" | observations at Sianfu |
| A.D. 581 | Chinese | 23° 41' 12" | observations at Sianfu |
| A.D. 584 | Chinese | 23° 41' 30" | observations at Loyang |
| A.D. 596 | Chinese | 23° 42' 12" | observations at Sianfu |
| A.D. 597 | Chinese | 23° 42' 12" | observations at Sianfu |
| A.D. 629 | Chinese | 23° 40' 07" | observations by Litchou-foung at Sianfu |
| A.D. 829 | Al Mamun | 23° 35' 00" | observations at Bagdad |
| A.D. 880 | Al Battani | 23° 35' 54" | observations at Rakka in Syria |
| A.D. 916 | Arab | 23° 35' 50" | mean of numerous Arab observations from A.D.829-1019 |
| A.D. 1000 | Ibn Junis | 23° 36' 11" | observations at Cairo |
| A.D. 1049 - 1052 | Chinese | 23° 33' 40" | observations as Kaifeng-fu |
| A.D. 1070 | Alzarkali | 23° 34' 42" | observations at Toledo |
| A.D. 1100 | Chinese | 23° 34' 32" | observations at Kaifeng-fu |
| A.D. 1130 | Chinese | 23° 31' 48" | observations at Hang Chow |
| A.D. 1140 | Almaeon | 23° 34' 12" | observations at Toledo |
| A.D. 1174 | Ben Maimon | 23° 31' 51" | observations at Cordova |
| A.D. 1250 | Alphonsine Tables | 23° 33' 11" | observations at Toledo |
| A.D. 1277-1280 | Chinese | 23° 33' 02" | observations by Ko-Chou-King at Peking |
| A.D. 1290 | Nasar-Al-Din | 23° 31' 40" | observations at Maragha (Persia) |
| A.D. 1290 | Guilliame de St. Cloud | 23° 34' 00" | observation at Paris |
| A.D. 1328 | Prophatius Judaeus | 23° 32' 42" | observations at Toledo |
| A.D. 1332 | Jean de Lignieres | 23° 33' 31" | observations at Paris |
| A.D. 1363 | Ibn al Shatir | 23° 32' 32" | observations at Cairo |
| A.D. 1437 | Ulugh Beigh | 23° 31' 44" | observations at Samarkand |
| A.D. 1460 | Purbach and Regiomontanus | 23° 30' 37" | observations at Erfurt, Nurnberg, and Vienna |
| A.D. 1468 | Toscanelli | 23° 31' 47" | observations at Florence |
| A.D. 1491 | Walther | 23° 30' 50" | observations at Nurnberg |
| A.D. 1491 | Novarra | 23° 30' 56" | observations at Bologna |
| A.D. 1514 | Werner | 23° 30' 33" | observations at Nurnberg |
| A.D. 1525 | Copernicus | 23° 30' 30" | observations at Frauenberg |
| A.D. 1570 | Ignatius | 23° 29' 00" | observations at Bologna (corrections uncertain) |
| A.D. 1570 | Dante Prince of Hess | 23° 31' 00" | observations at Cassel (corrections uncertain) |
| A.D. 1570 | Rothmann & Byrge | 23° 30' 20" | observations at Cassel (corrections uncertain) |
| MEAN | 23° 30' 07" | ||
| A.D. 1587 | Tycho Brahe | 23° 29' 49" | observations at Uraniborg |
| A.D. 1594 | Wright | 23° 30' 00" | observations at Cambridge |
| A.D. 1616 | Wendelin | 23° 30' 16" | observations at Forcalquier in the Basses Alpes |
| A.D. 1627 | Kepler | 23° 30' 30" | observations at Linz (Upper Austria) |
| A.D. 1636 | Peiresc | 23° 30' 23" | observations at Marseilles |
| A.D. 1636 | Gassendi | 23° 29' 58" | observations at Marseilles |
| A.D. 1650 | Riccioli | 23° 29' 40" | observations at Bologna |
| A.D. 1658 | Hevelius | 23° 29' 27" | observations at Danzig |
| A.D. 1664 | Cassini | 23° 29' 08" | observations at Bologna and Paris |
| A.D. 1686 | Wurzelbaur | 23° 28' 52" | observations at Nurnberg |
| A.D. 1660 | Montons | 23° 29' 03" | Hutton |
| A.D. 1672 | Richer | 23° 28' 52" | Hutton |
| A.D. 1686 | La Hire | 23° 29' 28" | Hutton |
| A.D. 1689.5 | Flamsteed | 23° 28' 56" | Ball's Astronomy |
| A.D. 1690 | Flamsteed | 23° 28' 48" | Encyclopaedia Britannica |
| A.D. 1690 | Flamsteed | 23° 29' 00" | Hutton |
| MEAN | 23° 28' 55" | ||
| A.D. 1703 | Bianchini | 23° 28' 35" | Encyclopaedia Britannica |
| A.D. 1703 | Bianchini | 23° 28' 25" | Hutton |
| MEAN | 23° 28' 30" | ||
| A.D. 1706 | Roemer | 23° 28' 41" | Hutton |
| A.D. 1715 | Louville | 23° 28' 24" | Hutton |
| A.D. 1730 | Godin | 23° 28' 20" | Hutton |
| A.D. 1736 | Condamine | 23° 28' 24" | Encyclopaedia Britannica |
| A.D. 1743 | Cassini de Thury | 23° 28' 26" | Encyclopaedia Britannica |
| A.D. 1750 | Lacaille | 23° 28' 19" | Encyclopaedia Britannica |
| A.D. 1750 | Bradley | 23° 28' 18" | Hutton |
| A.D. 1755 | Bradley | 23° 28' 15" | Encyclopaedia Britannica |
| A.D. 1756 | Mayer | 23° 28' 16" | Encyclopaedia Britannica and Hutton |
| A.D. 1769 | Maskelyne | 23° 28' 10" | Encyclopaedia Britannica and Hutton |
| A.D. 1772 | Hornsby | 23° 28' 08" | Hutton |
| A.D. 1779 | Nautical Almanac | 23° 28' 07" | Hutton |
| A.D. 1780 | Cassini | 23° 27' 54" | Encyclopaedia Britannica |
| A.D. 1795 | Maskelyne | 23° 27' 58" | Ball's Astronomy |
| A.D. 1800 | Nautical Almanac | 23° 27' 50" | Hutton |
| A.D. 1800 | Maskelyne | 23° 27' 57" | Encyclopaedia Britannica and Hutton |
| A.D. 1800 | Piazzi | 23° 27' 56" | Encyclopaedia Britannica and Hutton |
| A.D. 1800 | Pond | 23° 27' 56" | Hutton |
| A.D. 1800 | Delambre | 23° 27' 57" | Encyclopaedia Britannica and Hutton -- hundreds of observations |
| A.D. 1800 | Bessel | 23° 27' 55" | Ball's Astronomy |
| A.D. 1812 | English and French Astronomers | 23° 27' 42" | Hutton |
| A.D. 1813 | Pond | 23° 27' 49" | Encyclopaedia Britannica |
| A.D. 1813 | Brinkley | 23° 27' 50" | Ball's Astronomy |
| A.D. 1813 | Arago and Mathieu | 23° 27' 49" | Grant (History of Physical Astronomy) |
| A.D. 1815 | Bessel | 23° 27' 48" | Encyclopaedia Britannica |
| A.D. 1816 | Brinkley | 23° 27' 49" | Encyclopaedia Britannica |
| A.D. 1825 | Pearson | 23° 27' 44" | Encyclopaedia Britannica |
| A.D. 1835 | Airy | 23° 27' 40" | Encyclopaedia Britannica |
| A.D. 1850 | Leverrier | 23° 27' 32" | Encyclopaedia Britannica |
| A.D. 1868 | Airy | 23° 27' 22" | Ball's Astronomy |
| A.D. 1880 | Nautical Almanac | 23° 27' 17.6" | |
| A.D. 1900 | Nautical Almanac | 23° 27' 08" | |
| A.D. 1920 | Nautical Almanac | 23° 26' 58.9" | |
| A.D. 1940 | Nautical Almanac | 23° 26' 49.5" | |
| A.D. 1949 | Nautical Almanac | 23° 26' 45.3" |