• DOI:10.1177/002182869002100202
• Corpus ID: 117758864

An Analysis of Errors in the Star Catalogues of Ptolemy and Ulugh Beg

@article{Shevchenko1990AnAO,
  title={An Analysis of Errors in the Star Catalogues of Ptolemy and Ulugh Beg},
  author={Mikhail Shevchenko},
  journal={Journal for the History of Astronomy},
  year={1990},
  volume={21},
  pages={187 - 201}
}

• M. Shevchenko
• Published 1 May 1990
• Physics
• Journal for the History of Astronomy

The main peculiarity of Ptolemy's catalogue is the mean systematic error in the longitudes of the stars exceeding 1 • Many astronomers, in a European tradition going back to Tycho Brahe, I have considered the presence of such error to be an unambiguous indication that the catalogue was borrowed and modified rather than being a product of direct observations. Analysis of the fractional degrees of star coordinates by R. R. Newtonseemingly confirmed the artificial origin of the longitudinal shift as having been introduced by an erroneous precessional correction of 2 in every star longitude. However, there was an earlier alternative explanation. P. S. Laplace long ago drew attention to the highly unprecise value of the Sun's longitude, to which the positions of all stars were ultimately related.' The authenticity of Ptolemy's observation of Regulus as a reference star was confirmed by the results of a recent duplication of the observations with an armillary sphere by J. Wlodarczyk and J. Dobrzycki.' At the same time, James Evans has shown that the distribution of fractional degrees opens the way to a number of possible interpretations besides that of R. R. Newton.' Thus the inference that the catalogue in the Almagest is that of Hipparchus is not as well-established as might have appeared some time ago, and we may therefore return once more to the question of the authorship of this, the oldest extant star catalogue. Also, the investigation of the catalogue itself should be continued. Here the comparison of the catalogues of Ptolemy and Ulugh Begby Evans" seems very useful. Furthermore, the paper by Wlodarczyk? shows the investigation of the longitude errors to be very promising and it is this that forms the main subject of the present paper.