Introduction
Giuseppe Piazzi (1746–1826), was an Italian priest who also studied mathematics and astronomy. He taught theology and mathematics, founded an observatory in Palermo (Sicily) and became its director. I found more biographical details here.
Giuseppe Piazzi
Piazzi is known mainly for his 1801 discovery of the asteroid (now dwarf planet) Ceres, and for his star catalog [4] of 7646 stars (first edition 1803, second edition 1814). This catalog was "vastly superior to any that preceded it" according to Simon Newcomb [2, p. 381], thanks in no small part to the quality of the transit circle made for the Palermo observatory by English instrument maker Jesse Ramsden.
Several 19th and early 20th century works mentioned on the Ptolemy and Tycho pages refer to Piazzi's catalog, which is how it became interested in it. The catalog doesn't seem to have been put in machine-readable form so far (except a sample of it, part of James Lequeux's study [1] of 18th century catalogs) and I thought I might spare the task of doing so to other people interested in ancient star catalogs.
Catalog data
The file piazzi.dat contains Piazzi's star catalog [4] (1814 version), taking into account the corrections listed at the end of the book. Its format is specified in the ReadMe file and it is subject to automatic validation using the Anafile package of the VizieR service. Various observations about the original are gathered in notes.dat.
| File name | Explanation |
|---|---|
| ReadMe | File descriptions |
| piazzi.dat | Piazzi's catalog |
| notes.dat | Notes on Piazzi's catalog |
The catalog's fields are described in Latin in the introduction to the catalog. Unfortunately, I haven't been able to decipher much of it and, rather than making things up, I have left some of the field descriptions quite vague in ReadMe.
The star positions correspond to the beginning of year 1800 (Gregorian calendar), or
| Julian Day | 2,378,497 |
| Besselian epoch | B1800.0024… |
| Julian epoch | J1800.0054… |
Star identifications
Piazzi's catalog specifies a constellation for most stars. The obsolete constellations Custos Messium, Frederici Honores, Quadrans Muralis, Taurus Poniatovii, Triangulum Minus, Turdus Solitarius are used. The Pleiades and Anser (of Vulpecula & Anser) are treated as constellations. Norma is called Regula, and Navis covers Puppis and Vela. I made up abbreviations for the non-standard constellations, documented in notes.dat.
Cross-references to other catalogs
The catalog includes cross-references to other catalogs in the form of Bayer, Flamsteed, Hevelius designations, or numbers from some the most accurate catalogs of the time: Lacaille's southern stars catalog, Lacaille's zodiacal stars catalog [5], and Tobias Mayer's zodiacal stars catalog [3].
| File name | Explanation |
|---|---|
| notes_bid.dat | Issues pertaining to Bayer / Flamsteed / Lacaille letters |
| notes_fid.dat | Issues pertaining to Flamsteed designations |
| notes_name.dat | Comparison of Piazzi and IAU star names |
Bayer designations use the letter assignments from Flamsteed's and Lacaille's respective catalogs. The Bayer and Flamsteed cross-references contain many errors: wrong case, confusion between similar Greek letters, etc. I have attempted to identify and document these in notes_bid.dat and notes_fid.dat.
There are some issues with Lacaille's southern and zodiacal star number assigments as well. I have documented these at the end of notes.dat. I have not (yet) examined the cross-references to Hevelius's and Mayer's catalogs in detail.
Star names
Many Piazzi stars are identified by name. The table below lists the star names used in the catalog along with their modern versions according to the IAU Catalog of Star Names (version 2018-09-07).
The name is red if it differs, even if only in spelling, from the IAU one. The file notes_name.dat contains the same list, augmented with the stars unnamed by Piazzi that have an IAU name.
References
[1] James Lequeux, From Flamsteed to Piazzi and Lalande: new standards in 18th century astrometry, Astronomy and Astrophysics, Volume 567, July 2014. Related data gathered as VizieR's catalog J/A+A/567/A26.
[2] Simon Newcomb, A Compendium of Spherical Astronomy, New York: The Macmillan Company, 1906.
[3] Francis Baily, Mayer's Catalogue of Stars, corrected and enlarged; together with a Comparison of the Places of the greater part of them, with those given by Bradley; and a reference to every observation of every Star, Memoirs of the Astronomical Society of London, Vol IV, Part I, pp. 191–445. London: Priestley and Weale, 1830.
[4] Giuseppe Piazzi, Praecipuarum Stellarum Inerrantium Positiones Mediae Ineunte Saeculo XIX. Ex Observationibus Habitis in Specula Panormitana ab anno 1792 ad annum 1813. Palermo: Regia Typographia Militari, 1814.
[5] Éphémérides des mouvemens célestes, pour dix années, depuis 1765 jusqu'en 1775, et pour le meridien de la ville de Paris, Tome VI, Paris: Jean-Thomas Heissant, 1763. Catalogue des 515 Étoiles Zodiacales, observées en 1760 & 1761, par M. l'Abbé de la Caille, & réduites au commencement de l'année 1765, par M. Bailly, de l'Académie Royale des Sciences, pp. lxv-lxxvij.