William Herschel's catalog of Deep Sky objects
Thanks to Bill Arnett,
William Herschel's catalog is available online. Bill acknowledges
David Bishop for making it available.
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More material on Friedrich Wilhelm (William) Herschel:
William Herschel got interested in
systematically looking for, and observing, "nebulae" and star clusters when he
was presented a copy of the Messier Catalog
in December, 1781.
Up to that time, he had recorded observations of only 4 real and 2 non-existing
See a list of William Herschel's
Observations of Messier's Objects.
He started observing these objects in August, 1782, first observing globular
cluster M5 in Serpens on August 5.
By chance, he made his first own original discovery on September 7, 1782, of
the Saturn Nebula, NGC 7009.
There followed a time of researching how to do these observations, discoveries
and recordings most efficiently; during that time, William's siter
Caroline started to make a number of own
deepsky discoveries with her smaller Newtonian telescope:
look at her list (of eventually 20, including 8
original and 5 independent discoveries).
Astronomical League's selection of 400 Herschel objects, for which the
AL grants the Herschel Award. This list was compiled by
Brenda Branchett of Deltona, Florida.
full Herschel list of 2500 (actually 2514), which according to
David was originally compiled by
Fr. Lucian J. Kemble (1922-1999),
a Franciscan Friar then living in Cochrane, Canada, who later moved to
Lumsden, Saskaschewan, Canada, but the list partially lost;
(astronomer from England, now at ESO)
helped to restore. The list may still be somewhat buggy, though.
Moreover, besides these (mostly typing) errors, Herschel's list is indeed
considerably less reliable than Messier's smaller catalog:
Herschel's catalog contains 36 duplications, 4 entries belong to two objects
each, two further are listed twice as it is uncertain which object
corresponds to them, and 87 objects marked as nonexistent in our lists
(for whatever reason). Thus it seems that actually 2397 objects belong to
the total of 2520 entries in our list (some of these objects are still
multiple stars, or asterism).
- I have created a Herschel 2500 list sorted by Herschel number, available
in html (linked to our pages) or as
plain ascii file.
- I extracted the "Notes" on Herschel's catalog of
David Bishop from Bill's README
- Goto Bill Arnett's
complete Herschel directory.
Probably inspired by Caroline's unexpected success with her small instrument,
William looked for nebulae himself, and independently found the Tau Canis
Majoris cluster, NGC 2362, on March 4, 1783
(e.g., Hoskin 2005).
Eventually, he commenced a systematical survey with considerable effort,
assisted by Carioline, on October 23, 1783, with his 18.7-inch aperture,
20-foot focal length reflector, with standard magnification 157 and a field of
view of 15'4"; this telescope was used to discover most of William Herschel's
He made his next discovery on October 28, 1783: NGC 7184, Herschel's H II.1,
a little conspicuous galaxy in Aquarius of brightness 11.2 mag.
In only 1 1/2 years until April 1785, he cataloged 1000 deepsky objects, a
second catalog of 1000 objects followed to 1788 (published 1789), and a
further 500 objects to 1802. The final 8 objects found in 1802 remained
unpublished until 1847, when his son
John Herschel published them in appendix
to his catalog of observations made in South Africa
(John Herschel, 1847).
The accumulation of discoveries in the earlier years of search, the decrease
in the later 1780s, and the more occasional continuation thereafter, indicates
that Herschel's hunt for nebulae and clusters was not carried through to
"triumphant completion," but more an "unfinished business," as Michael Hoskin
recently reported (Hoskin 2005a,
Hoskin 2005b). This was due to the fact that after
an enthusiastic and fruitful start in 1784 and 1785, other work arose and took
more and more time, such as the construction of the great 40-foot reflector.
William's 1788 marriage, 1792 birth of son John, as well as other discoveries
and interests took even more time from the nebula project, so that finally
Caroline and William needed full 14 years for the final catalog of 500 objects,
leaving "un-swept" significant areas of the sky, in particular around the North
During this time, William Herschel also accumulated numerous
observations of most Messier Objects.
He invented the following classification scheme for nebulae and star clusters,
based on the appearance of these objects as he perceived them, rather than
William Herschel compiled his lists with running numbers for each object type.
Because of the missing physical meaning of this classification, it is of
historical importance only.
- Bright Nebulae
- Faint Nebulae
- Very faint Nebulae
- Planetary Nebulae
- Very large Nebulae
- Very compressed and rich star clusters
- Compressed clusters of small and large (i.e., faint and bright) stars
- Coarsely scattered clusters of stars
William Herschel was usually carefully avoiding to number the Messier objects,
in appreciation of Messier's prior work.
However, he of course numbered the missing
and the additional (i.e., later added)
objects, as he did not look at them as Messier's "nebulae." Erroneously, he
also numbered some of the Messier objects though, and in some cases, parts of
Look at the complete list.
Almost all of Herschel's objects (even the non-existing, erroneous entries)
have also obtained an NGC number; there are only
four or five exceptions.
As the most renowned astronomer of his time, William Herschel contributed
significantly to most branches of astronomy: Besides searching clusters and
nebulae, he also discovered planet Uranus in 1781, two satellites of Uranus,
Titania and Oberon, in 1787, and Saturn's moons Mimas and Enceladus in 1789,
he investigated the proper motion of stars and derived the peculiar motion of
the solar system toward the direction of constellation Hercules, modelled the
Milky Way galaxy from stellar statistics, established the common existence of
physical binary stars, and speculated about the nature of the nebulae,
including a discussion of the possibility of external island universes
(galaxies) which had been brought up by Kant. He also contributed to physics
(especially optics) and, e.g., discovered the infrared light.
Thanks to Arild Moland from Norway for contributing some corrections
to this page !
- William Herschel, 1786. [XXVII.]
Catalogue of One Thousand new Nebulae and Clusters of Stars.
By William Herschel, LL.D.F.R.S. Read April 27, 1786.
Philosophical Transactions of the Royal Society of London, Vol. LXXVI (76),
- William Herschel, 1789. [XX.]
Catalogue of a second Thousand of new Nebulae and Clusters of Stars;
with a few introductory Remarks on the Construction of the Heavens.
By William Herschel, LL.D.F.R.S. Read June 11, 1789.
Philosophical Transactions of the Royal Society of London, Vol. LXXIX (79),
- William Herschel, 1802. [XVIII.]
Catalogue of 500 new Nebulae, nebulous Stars, planetary Nebulae, and Clusters
of Stars; with Remarks on the Construction of the Heavens.
By William Herschel, LL.D.F.R.S. Read July 1, 1802.
Philosophical Transactions of the Royal Society of London, Vol. XCII (92),
- John Herschel, 1847.
Results of Astronomical Observations made during the Years 1834, 5, 6, 7, 8,
at the Cape of Good Hope. Smith, Elder and Co., London.
Here p. 128, Appendix. Places and Descriptions of Eight Nebulae discovered by
the late Sir William Herschel, but not published in his Catalogue.
Appendix to the Catalog of Nebulae and Clusters of Stars.
- Michael Hoskin, 2005.
William Herschel's Sweeps for Nebulae.
Journal for the History of Astronomy, Vol. 36, Part 2, No. 123, p. 230
- Michael Hoskin, 2005.
Caroline Herschel as Observer.
Journal for the History of Astronomy, Vol. 36, Part 4, No. 125, pp. 373-406
- Michael Hoskin, 2005.
Unfinished Business: William Herschel's sweeps for nebulae.
History of Science, Vol. 63, in press.
- Robert Smith, 1738.
A compleat system of opticks.
Other Deep Sky catalogs suitable for the
History of the Discovery of the Deepsky Objects
This webpage was selected as
Houston Astronomical Society Site Of The Week for
July 1, 2004
Last Modification: January 22, 2007