Sky & Telescope - June 2021 - 62

Active Imaging

or even an intervalometer if your camera doesn't have one
built in. The best option is a wireless intervalometer or cable
release, so that you don't accidentally tug the camera while
ﬁring off your exposures.

It's All in the Plan
Once you have your gear, you need to plan your shots. You'll
want to know where your chosen target will be relative to the
landscape or structure you hope to record it with. For example,
last July Comet NEOWISE (C/2020 F3) presented several great
deepscape opportunities. Since the comet was passing through
the north, low to the horizon late at night, I thought it would
be pretty cool to capture it above the Mackinac Bridge, which
connects the two parts of the state of Michigan. A shot like
this requires careful planning, because it deals with a small
ﬁeld of view. Add in the ever-changing position of the comet,
and it becomes even more challenging to compose the photo.
Luckily, there are tools available online and smartphone apps
to help pre-visualize your shot. I used the free online planetarium program The Sky Live (theskylive.com) to plan this image
and ﬁgure out when the comet was lowest to the horizon from
my chosen location.
The Mackinac Bridge spans from north to south as seen
from Mackinaw City, and I wanted to frame the comet
between the towers of the suspension bridge. Additionally, I
had to take into consideration the altitude of the comet from
where I planned to photograph - I didn't want it too far below

the bridge, or too high. According to the app, there were only
a handful of days in which this alignment would be the best. I
decided my best opportunity was on July 20th, when the comet
would appear precisely due north at about 3:12 a.m.
Next, I had to ﬁgure out if the landscape portion of the
scene worked compositionally. For this, I turned to the
smartphone app PlanIt Pro (yingwentech.com). This fantastic
tool lets you pre-visualize a shot with astonishing accuracy.
The app features constellation overlays, which are invaluable
for both nightscape and deepscape photography. And while
the app doesn't include transient objects like comets, its star
charts, combined with the position noted in The Sky Live,
allowed me to know the comet's precise location. On this
particular morning, NEOWISE was passing just below the Big
Dipper, which was helpful because its stars are visible even
with the bright lights of the Mackinac Bridge.
To use PlanIt Pro, you ﬁrst have to " pin " the exact location
where you plan to set up. Use the search feature to narrow
down your area, then hold your ﬁnger on the spot until a red
pin appears. Next, touch the camera icon, and you're ready to
set the focal length of your lens so the app can display your
camera's ﬁeld of view. Do this by tapping the lens value under
Focal Length and inputting your lens. Using my zoom lens, I
start with the wide-angle number to get my bearings, then I
" zoom in " to the focal length I plan to use in the next step.
With the lens set, tap the top left corner of the app to open
the Ephemeris Features and select Night Photography > Stars

Planning Ahead

S THE RIGHT TOOLS Planning images
that include a transient object like a rare
bright comet requires finding its exact position in the sky on the evening you intend
to photograph it. Most all planetarium
programs offer updates to include new
comets. This screen capture shows the
view as predicted by the online app The
Sky Live on the morning of July 20th, 2020.

JUNE 2 021 * SK Y & TELESCOPE

X FINDING YOUR SITE Several apps are available
in both the Apple and Google Play marketplaces to
help you precisely identify your location to get the
best image. This screenshot shows the view using
PlanIt Pro.
XX LAND AND SKY REFERENCE PlanIt Pro also
includes an option to display the bright stars and
constellation lines.

http://www.yingwentech.com http://www.theskylive.com

Sky & Telescope - June 2021

Table of Contents for the Digital Edition of Sky & Telescope - June 2021