THE PRACTICAL ASTRONOMER
becomes smaller and the binoculars become heavier.
Beyond a magnification of about 12, some sort of a
mounting or tripod is desirable. A word of warning, too:
every time you pick up the binoculars, even for a moment,
loop the safety-cord round your neck. Fail to do so, and
it is only a question of time before the binoculars are
dropped, with disastrous results.
The Moon is a constant source of enjoyment to the
binocular-user; the mountains, craters, valleys and rays are
beautifully brought out, and it takes very little time to
learn the main features. The Sun is emphatically to be
avoided (never use binoculars to look at it, even with the
addition of a dark filter), but there is plenty to see among
the stars. Binoculars bring out the diverse colours really
well; there are clusters, groups, rich fields, and nebulae.
And there is always the chance that we will be treated to
the spectacle of a bright comet. This has not happened
often in recent years, though of course the brilliant comets
Hyakutake (1996) and Hale–Bopp (1997) were spectacular.
These, then, are the first steps in home astronomy. If
your interest is maintained, it will then be time to consider
obtaining a telescope.Orion, photographed
over a saguaro cactus near
Tucson, Arizona, USA. This
photograph was taken by
David Cortner using a simple
hand-driven mounting which
tracks the stars by turning
a screw at the correct rate.Binoculars
Binoculars are graded
according to their
magnification and
their aperture, which
is always given in
millimetres. Thus a
7 50 pair yields
a magnification of
seven, with each
object-glass 50 mm
in diameter. If only one
pair is to be obtained,
this is probably a
wise choice, because
binoculars of this
type have a wide field
and are lightweight
enough to be ‘handy’.▼Star trails. Using an
ordinary camera, a standard
film and a long exposure, it
is possible to make pictures
of star trails, showing the
apparent movement of the
heavens. I took this picture
at La Silla, in Chile, in 1990.
The prominent trail to the
far left is Jupiter. The trail
above and to the right of
the dome is Betelgeux.eyepiecelensprismsH Atl of Univ Phil'03stp 7/4/03 6:20 pm Page 265