Sky & Telescope - October 2023 - 55

several 4×6 prints made with a 35-mm
camera and a 50-mm lens. Despite
including a fair bit of overlap between
each photo, it was impossible to make
the flat paper prints match to the
spherical shape of the night sky. This,
along with heavy vignetting at the edge
of each image, made for a rather sadlooking
photo project.
Fast-forward a few decades and it's
now possible to use the built-in panorama
features in image-editing software
to automatically apply the proper
corrections and merge the individual
frames into a single, seamless, wideangle
image. I find Adobe Lightroom the
easiest to use. Plus, it has the ability to
save your merged image as a DNG file,
which allows extensive post-processing.
Other options include Adobe Photoshop,
Affinity Photo, and PTGUI. Each of these
programs requires a significant amount
of overlap between the individual image
tiles to perform their digital magic, so
careful planning is important to ensure
the best results.
Each time you take a shot, pick a
star that's about one-third of the way in
from the edge of the frame and use it as
a reference point to line up the edge of
the next image in the sequence. You can
follow either a simple linear arrangement
or execute a cross-like pattern in
which the central image is surrounded
by additional frames on all four sides.
Even with a 50-mm lens on a fullframe
camera, you can quickly cover
impressively wide regions of the night
sky. However, as your lens focal length
increases, the process requires more
frames in order to cover the same field
of view and therefore takes substantially
longer to shoot.
You might be tempted to use the
absolute minimum number of shots
possible to photograph a given area, but
in my experience it's better to strive for
more coverage rather than less. A generous
amount of overlap ensures that you
won't discover any unsightly gaps when
you stitch together your frames.
Quick Tips
In the Northern Hemisphere, you
should start your shooting sequence
A QUESTION OF RESOLUTION This pair of cropped images of the region near Deneb, in Cygnus,
shows the dramatic difference in detail captured by a 50-mm lens (left) and a 15-mm fisheye
(right). Note how sharp the stars are and how well defined the nebulosity is in the 50-mm shot.
START SMALL If the thought of combining dozens of individual frames to create a
mosaic is overwhelming, take heart - you can always start with fewer images. This
portrait of the region near Deneb consists of just two overlapping frames captured
with an 85-mm lens.
with the westernmost edge of your
image set first. This allows you to maximize
your sky coverage before Earth's
rotation causes objects to sink into the
muck near the horizon or, worse, set
entirely. You don't want to be in a situation
where you have to rush your shots.
I'd also suggest shooting at least two
exposures for each tile in your matrix
just in case a passing satellite or aircraft
spoils one of them. It's even possible to
shoot the individual tiles over successive
evenings so long as sky conditions
remain consistent.
Desktop planetarium programs like
SkySafari are helpful for pre-visualizing
sk yand tele scope .o r g * OCTOBER 2023 55

https://skyandtelescope.org/

Sky & Telescope - October 2023

Table of Contents for the Digital Edition of Sky & Telescope - October 2023