The Caldwell Objects

(www.stsci.edu).
D i f N f e u b s u e l a e
The Deep Sky Field Guide to Uranometria
2000.0.
Sky Catalogue 2000.0, Vol. 2.
G a l a x i e s
Tully, R. Brent. Nearby Galaxies Catalog.
Cambridge, England: Cambridge University
Press, 1988. (types, angular sizes, distances,
masses, and luminosities)
The Deep Sky Field Guide to Uranometria
2000.0. (apparent magnitudes and surface
brightnesses)
NASA Extragalactic Database. Pasadena, CA:
Infrared Processing and Analysis Center.
http://nedwww.ipac.caltech.edu/. (positions
and, when not available from the above
references, other parameters)
E x t r a S g u a p l e a r c n t i o c v a e
"List of Supernovae." Cambridge, MA: Central
Bureau for Astronomical Telegrams.
http://cfa-www.harvard.edu/iau/lists/
Supernovae.html.
Note that World Wide Web Uniform Resource
Locators, or URLs, are subject to change.
The dimensions, magnitudes, and positions of
non-Caldwell objects generally were taken from
The Deep Sky Field Guide to Uranometria 2000.0.
Incidentally, the two-volume Uranometria 2000.0
atlas was radically revised as this book went to
press, as was its Deep Sky Field Guide companion;
descriptions of Uranometria 2000.0 charts refer to
previous incarnations.
Finally, in Chapter 2 and Appendix A the
Caldwell objects' celestial coordinates are stated
to varying degrees of precision. In each case the
decision was based on the object's angular
12
size and degree of concentration or symmetry
(tiny planetary nebulae merit arcsecond precision,
for example, while loose, 1°-wide open
clusters are listed to the nearest arcminute). The
coordinates should get each Caldwell object into
the field of view of a computer-driven telescope
or an equatorially mounted one being aimed with
the help of setting circles.
Incidentally, you'll note that I do not refer to
objects in this book as "C" objects, as in "C101." I
spell out the name "Caldwell." For the same
reason that Moore decided not to use the prefix
"M" (because that would conflict with the
Messier, or "M," objects), I decided not to call his
picks "C" objects either. As Archinal points out,
the "C" prefix has already been used for other
astronomical catalogs and is widely recognized
as a prefix designating star clusters. "The
Dictionary of Nomenclature of Celestial Objects .
. . shows 13 catalogs already designated by the 'C
name," he says. "In fact the Task Group on
Astronomical Designations of IAU Commission 5
specifically recommends... that among other
things, 'an acronym shall consist of at least three
characters.'" Thus for this book I have adopted
Archinal's recommendation, and use the full
Caldwell name. ("C" designations do appear on
the detailed finder charts and some photos for
brevity, however.)
SOME ORIGINAL SINS
This work corrects several unfortunate errors that
appeared in the December 1995 issue of Sky &
Telescope, where the Caldwell Catalog first was
published. In several cases the tabular
information (magnitudes, sizes, etc.) in this book
also differs significantly from that found in the
original Sky & Telescope presentation or on early
editions of the popular Caldwell Card. Here are
but a few of the most obvious errors that have
been corrected in this book.
Deep-Sky Companions: The Caldwell Objects