Sky and Telescope - March 2018 - 38

Imaging Aesthetics
u LUNAR ENCOUNTER
Close-ups of the lunar limb can
produce compositions with an
air of mystery. This mosaic of the
northeastern limb includes the
dark Mare Humboldtianum and
gives viewers the impression
they are flying over the edge of
the Moon themselves.

that are often depicted. The colors of deep-sky objects are
actually more pastel and subdued (watch for an article on
this subject in an upcoming issue). The most colorful things
we can see through a typical telescope are the stars, planets,
and the brightest planetary nebulae.
We are all guilty of pumping up the saturation for dramatic effect. That doesn't make it wrong, but there's a limit
to how far we can push the color saturation before it becomes
garish and detracts from the ﬁnal image. One way to avoid
over-saturating your images is to monitor the individual
color channels in your favorite image-processing program.
For instance, when increasing the saturation of an emission
nebula, pay close attention to the red channel. Make sure
that detail is still apparent in the brightest areas and doesn't
appear overexposed after your adjustments.

Composition

M A RCH 2 018 * SK Y & TELESCOPE

p SLIGHT TRAILS While deep-sky pictures require perfectly tracked
images that produce round stars, nightscape photos aren't as stringent.
This wide-angle, 30-second photo of the Turret Telescope at Breezy Hill
in Springfield, Vermont, looks quite nice even with slightly trailed stars.

cuts across the frame diagonally rather than straight across.
These considerations also apply when imaging the bright
planets. In particular, Jupiter offers more compositional
choices than the other planets due to its size, extremely
dynamic atmosphere, and retinue of Galilean moons, which
can add up to four additional smaller detailed objects to a
single composition.
Composing multiple adjacent targets in the same ﬁeld
presents its own challenges. Just because M108 and M97 in
Ursa Major can ﬁt in the opposite corners of your camera's
ﬁeld doesn't mean it makes for a good composition. Each
object in your image should have a comfortable space between
it and the edge of the frame whenever possible.
The same rules apply to nightscape photography. Balancing
your terrestrial and celestial targets in your picture frame is
how you unify the scene. If you're planning to shoot a young
crescent Moon alongside the Eiffel Tower, the photo might

SE A N WA LK ER / S&T (2)

Although composing an astronomical subject in an image can
be tricky, it's still an important aspect of the best astrophotos. Composition in astrophotography is tough because most
things in the night sky are so far away they are essentially
motionless, at least on a human timescale. You can't simply
move two star clusters closer together for that family portrait!
So take care when composing deep-sky astrophotos. A
perfectly tracked, well-processed image of a galaxy still looks
odd if the subject is placed too close to one side of the picture
frame. And a tiny planetary nebula in the middle of an image
surrounded by a nondescript star ﬁeld might have a better
impact if it were shot at an adequate image scale that resolves
lots of small-scale detail.
Spend time matching your target to your chosen equipment. There isn't much point spending an entire evening
shooting a secluded, distant galaxy just 30 arcseconds across
if your telescope and camera can only resolve 5-arcsecond
objects or larger. That galaxy will only be about 6 pixels across
in the ﬁnal image!
Another aspect of composition is how your target is placed
in the picture plane. A spiral galaxy like M104, the Sombrero
Galaxy, might present a more dynamic composition if you
rotated your camera slightly so that the long-axis of the target

Sky and Telescope - March 2018

Table of Contents for the Digital Edition of Sky and Telescope - March 2018