The Caldwell catalogue is an

astronomical catalogue An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, Galaxy morphological classification, morphology, origin, means of detection, or method of discovery. The olde ...

of 109

star cluster A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open cluster ...

nebula A nebula (; or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regions, such as in the Pillars of Creation in ...

e, and

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ...

for observation by amateur astronomers. The list was compiled by

Patrick Moore Sir Patrick Alfred Caldwell-Moore (; 4 March 1923 – 9 December 2012) was an English amateur astronomer who attained prominence in that field as a writer, researcher, radio commentator and television presenter. Moore's early interest in astro ...

as a complement to the Messier catalogue. While the Messier catalogue is used by amateur astronomers as a list of

deep-sky object A deep-sky object (DSO) is any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.). The classification is used for the most part by amateur astronomers to denote visually observed fa ...

s for observation, Moore noted that Messier's list was not compiled for that purpose and excluded many of the sky's brightest deep-sky objects, such as the Hyades, the

Double Cluster The Double Cluster, also known as Caldwell 14, consists of the open clusters NGC 869 and NGC 884 (often designated h Persei and χ (chi) Persei, respectively), which are close together in the constellation Perseus. Both visible to the ...

(

NGC 869 NGC 869 (also known as h Persei) is an open cluster located around 7,460 light years away in the constellation of Perseus. The cluster is around 14 million years old. It is the west component of the Double Cluster with NGC 884. NGC 869 and 884 ...

and

NGC 884 NGC 884 (also known as χ Persei) is an open cluster located 7640 light years away in the constellation of Perseus. It is the east component of the Double Cluster with NGC 869. NGC 869 and 884 are often designated h and χ Persei, respectively. ...

), and the Sculptor Galaxy (NGC 253). The Messier catalogue was actually compiled as a list of known objects that might be confused with comets. Moore also observed that since Messier compiled his list from observations in Paris, it did not include bright deep-sky objects visible in the Southern Hemisphere, such as

Omega Centauri Omega Centauri (ω Cen, NGC 5139, or Caldwell 80) is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of , it is the largest known globular clus ...

, Centaurus A, the

Jewel Box Jewel box or Jewel Box may refer to: * Jewelry box, a container for gemstones Places or architecture * Jewel Box (St. Louis), listed on the NRHP in Missouri * Jewel Boxes, a name for eight banks designed by architect Louis Sullivan *Jewel Box ...

, and 47 Tucanae. Moore compiled a list of 109 objects to match the commonly accepted number of Messier objects (he excluded M110), and the list was published in ''

Sky & Telescope ''Sky & Telescope'' (''S&T'') is a monthly magazine covering all aspects of amateur and professional astronomy, including what to see in the sky tonight and new findings in astronomy. Other topics covered include: *observing guides for planets, ...

'' in December 1995. Moore used his other surname – Caldwell – to name the list, since the initial of "Moore" is already used for the Messier catalogue. Entries in the catalogue are designated with a "C" and the catalogue number (1 to 109). Unlike objects in the Messier catalogue, which are listed roughly in the order of discovery by Messier and his colleagues, the Caldwell catalogue is ordered by

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

, with C1 being the most northerly and C109 being the most southerly, although two objects ( NGC 4244 and the Hyades) are listed out of sequence. Other errors in the original list have since been corrected: it incorrectly identified the S Norma Cluster ( NGC 6087) as NGC 6067 and incorrectly labelled the Lambda Centauri Cluster ( IC 2944) as the Gamma Centauri Cluster.

Reception

The Caldwell Catalogue has generated controversy in the amateur astronomy community for several reasons. * Moore did not discover any of the objects in his catalogue which are often very well known objects and not 'neglected' as claimed by Moore. * Its presentation as a catalogue with distinct designations, rather than a list, potentially may cause confusion amongst amateur astronomers as the 'C' Designation is not commonly used. * The list was promoted as an extension of the Messier Catalogue, however the objects are often arbitrary with many easily viewable objects omitted while some objects not readily available to visual observers are included. Caldwell advocates, however, see the catalogue as a useful list of some of the brightest and best known non-Messier deep-sky objects. Thus, advocates dismiss any "controversy" as being fabricated by older amateurs simply not able or willing to memorize the new designations despite every telescope database using the Caldwell IDs as the primary designation for over 25 years. NASA/Hubble also lists the 109 objects by their Caldwell number.

Caldwell star chart

Number of objects by type in the Caldwell catalogue

Caldwell objects

References

External links