The Caldwell Objects

most striking specimen. Its beak is yellow, its
head a rose-tinted aquamarine, its body olive, its
wings vibrant indigo, and its tail feathers squidink
black. You must see it! Now imagine the
disappointment when you go birding with a
friend, who points out the black raven. Shocked,
you show your friend the photograph in your
guidebook. Your friend laughs and tells you that
that's a heavily enhanced image that exaggerates
the iridescence of the bird's feathers.
The point is, why risk disappointing new
observers when we can try to help them discover
the beauty of reality? Furthermore, you most
likely will compare the photographs to your
eyepiece views with the help of a dim red
flashlight, and under such illumination a color
photograph actually would be a handicap.
Whenever possible, photographs were
chosen to reflect the kinds of detail an observer
might see with his or her own eyes. For that
reason a few photographs may appear underexposed
compared to more famous views you
may have seen elsewhere.
That we were able to reproduce such excellent
photographs of the Caldwell objects is
largely a result of the generosity and perseverance
of many talented astrophotographers. These
dedicated students of the night sky work much
harder than a purely visual observer might
imagine in order to capture their revealing
images.
While we attempted to obtain high-quality
astrophotos of every Caldwell object from the
worldwide community of amateur astronomers,
in several cases we have resorted to reproducing
digitized photographs taken by enormous
Schmidt telescopes in both hemispheres. These
photos have been made available to astronomers
and scientists worldwide by the visionary
architects of the Digitized Sky Survey (DSS),
which can be perused on the World Wide Web
16
at http://archive.stsci.edu/dss/. (The copyright for
the DSS photos used in this book rests with the
Anglo-Australian Observatory Board, the United
Kingdom Particle Physics and Astronomy
Research Council, the California Institute of
Technology, and the Associated Universities for
Research in Astronomy; they are used here with
permission.) Detailed credits appear in Appendix
D.
In a few cases we have also reproduced
images from the Hubble Space Telescope and
large telescopes like those on Mount Wilson and
Palomar Mountain. For the most part, these
images are included to illustrate scientific points
discussed in the accompanying essays.
THE DRAWINGS
All the sketches in Chapter 2 are composites of
field drawings I made at various magnifications.
They are shown approximately with north up
and west to the right, unless otherwise noted.
Whenever possible, the orientation matches that
of the corresponding photograph. Scale bars are
included to help you size up each object in your
own telescope. (Note that the scale of a drawing
might differ markedly from that of the
accompanying photograph; if so, a scale bar will
appear on both the photograph and the drawing.)
The composites show details visible at low,
medium, and high magnifications. For instance,
on the one hand, I might have seen a galaxy's
faint halo readily at low power but not at high
power. On the other hand, a small knot in that
galaxy's arm might have been obvious at high
power but inconspicuous at low power. Both the
halo and the knot will appear in my sketch.
The drawings also show details seen in fits
and starts over several hours observing from a
dark-sky site. Some objects — like the Eta
Carinae Nebula, the Coalsack, and the Bubble
Nebula, among others — required several
Deep-Sky Companions: The Caldwell Objects