De Chéseaux's List of 21 "Nebulae"

The Swiss astronomer and mathematician Philippe Loys de Chéseaux (1718-51) became known because of his discovery and observations of the famous comet of December 1743 to March 1744, which became very brilliant, exposed six tails, and also impressed 13-year-old Charles Messier in his Lorrainian hometown, Badonviller.

About in 1746, he also observed several clusters and "nebulous stars", and compiled a catalog of their positions. According to Kenneth Glyn Jones, 8 of them were original discoveries: IC 4665 (No. 2, maybe doubty), NGC 6633 (No. 3), M16 (No. 4), M25 (No. 5), M35 (No. 12, but this one might have seen before by John Bevis in England), M71 (No. 13), M4 (No. 19), and M17 (No. 20). Moreover, he independently re-discovered M6 (No. 1), NGC 6231 (No. 9, together with stars z1 and z2 Scorpii) and M22 (No. 17).

De Chéseaux's list was given to Reaumur, who presented it to the French Academy of Sciences on August 6, 1746, but it was not otherwise published, although mentioned by Le Gentil (1759). It was investigated by Guillaume Bigourdan in 1884 and became more wellknown only then (Bigourdan 1892).

We have a translation of De Chéseaux's original list online.

A list of identifications of De Chéseaux's objects follows:

de Chéseaux    Messier/NGC/IC      Remarks

No. 1 M 6 (!) No. 2 IC 4665 ? ! No. 3 NGC 6633 ! No. 4 M16 ! No. 5 M25 ! No. 6 NGC 869, h Per No. 7 NGC 884, Chi Per No. 8 M 8 No. 9 NGC 6231+z1,z2 Sco (!) No. 10 M 7 No. 11 M44 No. 12 M35 !? No. 13 M71 ! No. 14 M11 No. 15 M31 No. 16 M42 No. 17 M22 (!) No. 18 NGC 5139, Omega Cen No. 19 M 4 ! No. 20 M17 ! No. 21 [M13] - not seen
An exclamation mark notes an original discovery, if in parentheses, an independent rediscovery. The discovery of the non-Messier objects NGC 6633 and IC 4665 is mentioned in the Webb Society Deep-Sky Observer's Handbook, Volume 3 (Open and Globular Clusters) p. 3. De Chéseaux lists M13 with the remark he had not yet found it.

Besides observing nebulous patches in the sky, de Chéseaux was among the first to formulate Olbers' paradox (previous thinkers in that direction include Johannes Kepler and Edmond Halley).


  • History of the Discovery of the Deepsky Objects
  • More Deepsky Catalogs and Observing Lists
  • Some other historical catalogs
  • De Chéseaux's original list (newly translated as Fredi de Maria's former Version seems to be unavailable)
  • De Chéseaux short biography

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: April 15, 2000