"Historic ZC" - Explanation

Dr Wolfgang Steinicke

13 April 2021

perhaps few people have ever heard of Caroline's masterpiece, the Zone Catalogue, for which she was awarded in 1828 with the Gold Medal of the Astronomical Society of London (later Royal Astronomical Society). After William's death and her return to Hanover, Caroline started a monumental task: the compilation of all Herschel objects (nebulae & clusters) - found between 1783 and 1802 in 1112 sweeps and published in three catalogues - into a single item. Because the printed version offers only relative positions to reference stars, she calculated coordinates for 1800. Moreover, Caroline listed all observations, made for each object, often with different reference stars. All entries were arranged in zones of constant 'polar distance' (PD) and ordered by AR and observation date within. The resulting Zone Catalogue, finished in 1825, has 4050 entries for 2501 objects. It lists 3551 observations, using 1134 different reference objects (in most cases Flamsteed stars). My revised version contains 45 additional entries (objects and observations).

The Zone Catalogue was mainly made for John Herschel, who took it as the basic dataset for his observations at Slough. In the sweep campaign, made between 1825 and 1833 with an 18.25-inch reflector, he tried to reobserve the non-stellar objects, found by his father. He was successful and even found 510 new objects. The result was published in the Slough Catalogue of 1833.

The reason, why Caroline's monumental Zone Catalogue is so barely known is simple: it was never published! Her handwritten manuscript is archived at the Royal Society, London. Of course, for my reserach on Herschel, I made a good copy some years ago - and began to analyse its content. The result is the first publication of Caroline's awarded work after nearly 200 years!

The the revised Zone Catalogue not only offers Caroline's data but a lot of additional information, like the identification of the reference stars and modern object data. It is a by-product of my detailed examination of Herschel's observations. The objects in my file are sorted by PD zone and Caroline's 'General Number' (1 to 2500), assigned to the Herschel objects, according to their discovery date. Click here for download (zipped xls-File). All information presented here is part of my scientific research. The results can be found in my upcoming book William Herschel - Discoverer of the Deep-Sky. The epochal work of the greatest visual observer and his talented sister Caroline.

The data presented here are copyright by the author. When used in a publication or in other datasets, this must be credited properly (please inform me in any case). Please also inform me about errors found in the datasets.


"Historic ZC" columns (bold = from Zone Catalogue, italics = added by me)

Ad Added entry, not in original Zone Catalogue: a = 11 added objects, s = 34 added observation (sweep) of already catalogued object
Zone Polar disctane zone: PD 0 to 121
GN Caroline Herschel 'General number' = object number by discovery date (1...2500)
Class Herschel designation: class (I...VIII) and running number in each class
Cat Entry in Herschel catalogue (1, 2, 3)
Date Discovery date as given in Herschel's published catalogues (year, month, day)
Star Reference star or object
Src Source: F = Flamsteed, B = Bode, H = Hevelius, L = Lacaille (southern star), M = Mayer (Zodiacal Catalogue),    W = Wollaston, O = Caroline's catalogue of omitted Flamsteed stars, N = nebula,
DS = double star, * = other, x = no object mentioned, z = no object. The information of this column is included in column 'Star' in the Zone Catalogue.
M, S, D, M Relative position. f/p = non-stellar object follows/precedes the reference object ('Star') by M (minutes) and S (seconds) in RA; n/s = non-stellar object is north/south the reference object ('Star') by D (degrees) and M (arcminutes) in PD.
Caroline's 1800 position for the Herschel object: right ascension (hours), polar distance (degree)
Sweep Sweep number (42 - 1112)
Obs Number of observations
n Different reference stars used for a single observation (n = 1...4)
HD Star in Henry Draper Catalogue
V* Visual magnitude of reference object
Con* Constellation of reference object
NGC NGC- or IC-number
M Identity with other class object(s)
h No. in John Herschel's Slough and Cape Catalogues
GC No. in John Herschel's General Catalogue
Identity Identity with other object; class or GN (sweep)
Right ascension (hours) and declination (degrees) of the non-stellar object for 2000
Visual magnitude (from Revised NGC/IC)
Constellation of non-stellar object (from Revised NGC/IC)
Object type (from Revised NGC/IC)
Object status: 1 = galaxy, 2 = galactic nebula, 3 = planetary nebula, 4 = open cluster, 5 = globular cluster, 6 = part of nebula, 7 = NGC dublicate, 9 = star(s), 10 = not found
Discoverer Discoverer of non-stellar object (if found before Herschel)