Skywatch - 2021 - 78

Intro to Imaging

Tracking the Sky
To take deep images of the night sky
that show sharp, round stars, you'll need
a tracking mount to compensate for
Earth's rotation. If you have a telescope
with a motorized equatorial mount, you
can simply attach your camera on top
of the telescope and do what's known
as pigg yback astrophotography. This works
well, but there are some drawbacks to
be aware of. The biggest problem is that
you can't use your telescope to look at
anything else while you're taking the
picture. Fortunately, new options are
available that don't involve a big, heavy

telescope mount. I'm talking about
so-called tracking heads that attach
between your photo tripod and camera.
Many companies make such devices,
including AstroTrac (astrotrac.com),
iOptron (ioptron.com), Losmandy
(losmandy.com), Sky-Watcher (skywatcher.com), and Vixen (vixenoptics.com). Omegon (omegon.eu) even
oﬀers an inexpensive, wind-up model -
no batteries required!
With a tracking mount, you can also
use telephoto lenses with your camera to
take close-ups of faint nebulae, star clusters, or big, bright galaxies such as M31
or the Magellanic Clouds.
Keep in mind that any tracking
errors in your mount will be magnified
by your lens's focal length. For example,
with a 50-mm lens, I can shoot 5-minute
exposures on a portable tracking mount,
but I begin to see elongated stars when
using a 180-mm lens and exposures
longer than about 1 minute. Knowing
this, I can combine a bunch of 1-minute
exposures to produce great results when
shooting bright objects.
As with most astronomy, the sky is
literally the limit. If you desire even

greater resolution than you can get with
basic equipment, replace the eyepiece
on your telescope with your DLSR or
MIL camera and dive into the world of
prime-focus astrophotography. This is
advanced stuﬀ, however, and beyond
the scope of an introductory article.
Once you master the basic techniques
described here, you'll have a great shot
at trying out more sophisticated imaging methods. (You can visit https://
is.gd/Astrophotography to learn
more about advanced astrophotography
techniques.) But you might be content to
keep things simple. After all, the popular astrophotographers who are members of The World at Night organization
(twan.org) shoot with nothing more
than what I've described here.
For now, grab your camera or cell
phone and experiment using these easy
tips. There's a good chance you'll come
home with some really pleasing images
on your very fi rst night.
Sky & Telescope Associate Editor
SEAN WALKER images the night sky
from various locations throughout
southern New Hampshire.

p Special-Use Camera If you grow beyond introductory techniques,
consider acquiring a dedicated astro-camera. They're designed exclusively
for imaging astronomical subjects and attach to your telescope in place of an
eyepiece. In this way, you can record deep images such as this shot of the
famous Horsehead Nebula and its surrounding nebulosity.
t Star

Trails A series of long exposures on a tripod produces a star trail
photo showing the apparent movement of the stars as the Earth rotates on its
axis. This photo shows 15 minutes of trails with Polaris, the pole star, at left.
78 SK Y WATCH 2021

HORSEHEAD: MASIL IMAGING TEAM

an f/2 lens will record star clouds in the
Milky Way and even bright galaxies in a
20-second exposure.
With a DSLR or MIL camera and
a shutter-release cable, you can use the
"bulb" mode to hold the shutter open
indefi nitely, eliminating the need to
combine many shorter exposures to
create star trail photos. With a suitable
wide-angle lens, you can even use bulb
mode and a tripod to record an entire
lunar eclipse in a single unique image,
revealing the shape of Earth's shadow.

http://www.astrotrac.com http://www.ioptron.com http://www.losmandy.com http://www.sky-watcher.com http://www.vixenoptics.com http://www.sky-watcher.com http://www.vixenoptics.com http://www.omegon.eu https://www.is.gd/Astrophotography.com https://www.is.gd/Astrophotography.com http://www.twan.org

Skywatch - 2021

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