Sky & Telescope - February 2020 - 27

A Good Plan
The ﬁrst thing needed to capture deep images of nebulae, galaxies, and star clusters over an attractive foreground is a ﬁrm
knowledge of the night sky. Sure, the Orion Nebula, Andromeda Galaxy, or Magellanic Clouds are obvious deepscape
targets, but there are many other objects that can expand your
subject matter and add variety to your work. Virtually every
major constellation offers something to focus on.
Knowing where an object will rise above the horizon can
help you plan a composition before it's ready to photograph.
A planetarium app can help give you a general idea of where
an object is going to rise, but placing the sky in context to the
landscape you intend to shoot requires more specialized tools.
Several apps are available to aid in planning your composition. The Photographer's Ephemeris (photoephemeris.com),
PhotoPills (photopills.com), and PlanIt! (yingwentech.com)
are some of the powerful tools available online or downloadable as Apple and Android apps that can help you to plan
exactly where to position yourself so that your subject rises
precisely above the foreground as you envisioned it. Most of
these apps use built-in planetariums that combine a night sky
map and a Google Earth view of your chosen location.
Transient objects such as comets require you to monitor astronomy websites to get up-to-date information about
where these moving targets will be in your sky as they
brighten enough to photograph in a single exposure.

Choosing a Lens
Deepscape photography is more challenging than typical
nightscapes in that you often use telephoto lenses with narrower ﬁelds of view. This means that you can only shoot for a
short time before your subject becomes noticeably trailed. But
a good choice for starters is a high-quality, fast prime-focus
35-mm or 50-mm f/1.4 lens that produces sharp star images
when used at its widest aperture. I recommend that you stop
the lens down to f/2 to reduce aberrations in the corners of
the frame. Stopping down the lens also reduces vignetting
to nearly imperceptible levels. Most recent full-frame DSLR
and mirrorless cameras have decent noise characteristics.
But the newest models tend to incorporate the latest sensors,
which produce excellent images
at the extremely high ISO speeds
needed to "freeze" the motion of
your target over a landscape in
short exposures.
A handy rule of thumb for
nightscape photography is known
as "the rule of 500." This states
that for a ﬁ xed (non-tracking)
camera, 500 divided by the focal
length of your lens in millimeters
gives the length of an exposure
in seconds before stars appear
trailed in your image. (And that
also applies to the appearance

p Apps such as The Photographer's Ephemeris help
you plan your deepscape
images by plotting the
direction where specific targets will rise or set above
the horizon based on your
exact location.

q High-quality, fast lenses
such as Sigma's Art lens
series combined with the latest sensors will produce your
best results.

sk yandtelescope.com * FEBRUARY 2 02 0

http://www.photoephemeris.com http://www.photopills.com http://www.yingwentech.com http://www.skyandtelescope.com

Sky & Telescope - February 2020

Table of Contents for the Digital Edition of Sky & Telescope - February 2020