Sky and Telescope - April 2016 - 66

Celestial Imaging

Choosing a Camera

The question isn't which is best, but which is best for your goals.
IT'S NEVER BEEN a better time to take up astrophotography. A good amateur image today would have been
award-winning and groundbreaking only 10 years ago,
and a half century ago no one would have believed it was
a real photograph - because even shots from professional observatories were inferior. Advances in optics,
mounts, and cameras have all contributed to the golden
age of imaging we live in today, but the technology can
be bewildering to the newcomer.
This article isn't about which camera to buy but rather
attempts to explain the buzzwords and performance
metrics used to evaluate camera models today. There's
no such thing as the "best camera" on the market. The
real best camera is constrained not only by your budget
but also by your imaging goals (what you intend to shoot)
and which optics you'll be pairing it with. Matching a
camera to your glass is just as important as other criteria
when choosing a camera. So let's have a closer look.

Telescopes 101
Although most people associate a telescope with the concept of magniﬁcation, the main purpose of a telescope
or camera lens is actually to gather light. The bigger the
66

April 2016 sky & telescope

MANY CHOICES With so many cameras to choose from today,
how can beginners decide which one best suits their needs?

opening, or aperture, the more light can come in. This
is the ﬁrst principle of photography - no matter which
camera you choose, more light is always a good thing.
Regardless of whether we're talking about a camera
lens, refractor, reﬂector, or catadioptric, we measure an
optics ability to collect light by its aperture. This is simply how wide the front opening is that lets in the light (or
the size of your primary mirror).
Magniﬁcation is determined by your optics focal
length. Less magniﬁcation makes the image smaller but
brighter. Think of light as sand pouring out of a bag. In
5 minutes of exposure time you only get so much sand,
and you can make a big, wide, but thin pile of sand, or
a small but deep pile of sand. Deep piles of sand (more
light) produce brighter images and an improved signalto-noise ratio. If you want a wide and deep pile of sand,
you have to expose longer or get a bigger aperture with
the same focal length.
The next important metric in understanding a scope
or lens is its focal ratio, usually indicated by the designa-

Sky and Telescope - April 2016

Table of Contents for the Digital Edition of Sky and Telescope - April 2016

Contents
Sky and Telescope - April 2016 - Cover1
Sky and Telescope - April 2016 - Cover2
Sky and Telescope - April 2016 - 1
Sky and Telescope - April 2016 - Contents
Sky and Telescope - April 2016 - 3
Sky and Telescope - April 2016 - A
Sky and Telescope - April 2016 - B
Sky and Telescope - April 2016 - 4
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Sky and Telescope - April 2016 - Cover3
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