Astrophotography (literally photographing stars, but
it usually includes all kinds of celestial bodies,
such as nebulae and galaxies)
is a great hobby, but it can be quite challenging
for the beginner. However, with a bit (lot) of patience
and the right equipment most difficulties can be
overcome. Here's a brief introduction;
1. Camera
The first thing you'll need is a
single lens reflex (SLR) camera, with
either a long exposure setting or a
manual shutter release. Compact cameras
are unsuitable, as they
usually lack the possibility to do
long exposure or manual shutter release,
and getting the right focus might be
problematic as well.
2. Mount
The next step is to get a stable mount for the
camera. Since we're talking about very low
light levels, you'll need a camera that can
cope with long exposure times. With long exposure
times, however, the image is very susceptible
to vibration and movement, and it's easy to end
up with bright streaks instead of stars. And,
to complicate things further, the celestial sphere
rotates (15 degrees per hour), so when dealing with
exposure times of more than, say, 30 seconds,
you actually need to rotate the camera along with
the sky. See below.
When taking pictures you can rest
the camera against anything solid,
such as the car, or place it on the
ground in a stable position. It's
recommended to get a tripod, though,
as you'll have much better control of the
aim and field of view.
3. Barn door mount
If you want to take shots of really dim
objects, such as nebulae, clusters,
comets and galaxies,
or just generally spice up your pictures,
you might need to use exposure times of
anything from several minutes, perhaps
up to a few hours.
But as mentioned, the sky rotates, so we'll
need something that rotates
along with it. The "barn door mount" to the
rescue!
Making your own barn door mount is pretty
easy. You'll need two pieces of wood,
a good hinge, some screws and a
ball-and-socket camera mount. The two
pieces of wood are joined by the hinge,
the camera is mounted on the top side, and
the tripod is mounted underneat.
(If you search the net for "barn door mount"
you can easily find more detailed
building plans.)
The principle is the same as with
a telescope on an equatorial mount;
if you point
the axis of the hinge towards the
pole star, the "door" will
"swing open" in the same direction as the sky
rotates.
You will need to use a screw to control the
angle, though, as you need to be pretty
accurate.
4. Taking it up a notch
More experienced astrophotographers might try
different approaches, such as "piggybacking",
i.e. mounting your camera onto the tube
of a telescope, photographing through the
telescope (adapters can be found for most
cameras), and digital photography using
either a regular digital camera or a
CCD camera specialized for low light levels.
Other tricks of the trade include
filters, to remove unwanted light pollution
or to emphasise certain parts of the
spectrum.
5. Conclusion
All in all, it doesn't have to be very
difficult, nor expensive, but it will
take a bit of trial and error.
But the reward for patience is
stunning pictures, and impressed
friends.