OF THE ROGER N. CLARK

VISUAL ASTRONOMY OF THE DEEP SKY
charts but renders most objects too small to
show much detail. The book was designed for
the purpose of finding faint objects, and at
this it succeeds superbly.
Webb Society Deep-Sky Observer's Handbooks,
compiled by the Webb Society, Kenneth
Glyn jones, editor (Enslow Publishers, Hillside,
Nj, and Lutterworth Press, London,
1979-1987). Published in seven volumes:
1 Double Stars
2 Planetary and Gaseous Nebulae
3 Open and Globular Clusters
4 Galaxies
5 Clusters of Galaxies
6 Anonymous Galaxies
7 The Southern Sky
This series is a fine addition to the serious
amateur observer's reference collection. Each
volume has descriptions and drawings of
many objects, including many that are rarely
described. Volume 5, Clusters of Galaxies,
covers a topic not fo und elsewhere in amateur
literature. Unfortunately, each book is quite
expensive for a paperback, the text is reproduced
from typewriter manuscript, and the
drawings tend to be reproduced poorly and
too small. Often it is hard to correlate a
sketch with a photograph.
Edmund Scientific (10 1 East Gloucester
Pike, Barrington, Nj 08007, USA) published
a series of short paperback books on astronomy
in the mid 1960s, all written by Sam
Brown. The following is a list:
Homebuilt Reflector Telescopes. 36 pages. Cata_
log no. 9066
Photography With Your Telescope. 36 page s.
Catalog no. 9078
How to Use Your Telescope. 36 pages. Catalo g
no. 9055
Time in Astronomy 36 pages. Catalog no. 9065
Mounting Your Telescope. 36 pages. Catalog no .
9082
Telescope Op tics. 32 pages. Catalog no. 9074
The above books were compiled into one
work with only a few omissions:
All About Telescopes. 192 pages. Catalog no.
9094
These books describe nearly all aspects of
the use of a telescope, finding objects in the
sky, the use of setting circles, photography
and even making your own telescope. Th
text is clear and many information-packed
figures appear throughout. Students in grade
school or junior high can easily understand
most of the concepts. These books are highly
recommended for the beginning amateur
astronomer. The price is also less than most
books on the market today, costing less than
one low-grade eyepiece.
The books are, however, dated. The title
"All About Telescopes" implies material on
many types, hut Schmidt-Cassegrains, popular
today, are not mentioned. Also the sections
on photography do not discuss modern
films. In spite of this they are a good source of
basic material for the beginner.
Appendix B
Star clusters for finding your
limiting magnitude
On the following pages are maps of open star
clusters whose individual stars have had their
magnitudes determined by Hoag et al. (1961).
For each cluster, two charts are presented:
one showing stars labelled with their visual
magnitudes; the second, on the facing page,
with stars only. Magnitudes are given to the
nearest tenth, with the decimal point omitted
so it won't be confused with a faint star.
Thus, magnitude 12.2 is written 122.
Most magnitude labels are placed to the
upper right of each star, the same distance
from the center of the star dot regardless of
the dot size. In some cases, crowding required
the label be above or to the left of the
star. Occasionally, the label had to be put
below the star. By remembering these rules,
and by refering to the key for star sizes with
each chart, every magnitude label can be
matched to the correct star - even when the
label is closest to a different star.
Chapter 4 discusses in more detail how to
use the charts to determine your telescope's
limiting magnitude on a given night. In particular,
avoid using faint stars close to other
stars, especially bright ones. Magnification
strongly affects the visibility of faint stars;
each chart lists viewing distances from the
page that correspond to various magnifications
in a telescope (see Chapter 5 and equation
5.2).
North is up and astronomical east is to the
left on each chart. The scales on the sides are
approximate offsets in arc-minutes from a
star that was selected to be the chart's center.
These offsets are not exactly right ascension
and declination. True lines of right ascension
on these charts would converge slightly toward
the poles, and most true declination
lines would be slightly curved. But these
effects are small, and for ordinary visual purposes,
the "X" direction can be considered
right ascension and the "Y" direction declination.
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