Sky & Telescope - August 2020 - 67

W The app
includes a
wealth of
information on
every clickable target,
including
a detailed
description
(far left) and
a data table
that includes
information
specific to
your location,
such as rising,
transit, and
setting times
(near left).

designs. Swapping these out for several
of my own quality Plössls noticeably
improved the view.
The scope also includes a 90° erectimage diagonal that uses an Amici
prism. While this diagonal renders an
image that matches the orientation
of the app's display, it also noticeably
degrades the view by introducing a
vertical diffraction spike on bright targets, especially when using the 10-mm
eyepiece. This was most annoying when
observing Venus in a dark sky. Replacing this prism diagonal with a 2-inch
mirror diagonal eliminated the problem, allowing me to clearly see diffraction rings around bright stars. Stars
appeared fairly symmetrical on both
sides of focus, with the noticeable purple fringe expected for a relatively fast
achromat. This chromatic aberration
was only obvious on the brightest stars
and on Venus, Jupiter, and the Moon.
It was easily overlooked on everything
else. I often forgot I was observing
through an achromat as I enjoyed the
view of several double stars, particularly
24 Comae Berenices and Castor.
One other shortcoming of the StarSense Explorer is the long damping time

after touching the scope. It usually took
5 to 6 seconds before vibrations settled
down enough to judge whether I had
tweaked the focus properly or whenever
I touched the slow-motion controls.
Damping improved slightly by keeping
the tripod legs extended only about half
way and observing while seated, but
overall I felt the telescope was undermounted. Swapping the OTA with a
smaller though heavier refractor I own
only increased the vibration problem.
At times I had an issue that was more
to do with my smartphone. Sometimes
the app had a hard time verifying the
initial calibration target, which during
this past winter and spring evenings
tended to be Venus. The problem turned
out to be ﬁngerprint smudges on the
camera's lens window due to its proximity to the ﬁngerprint reader normally
used to wake up the phone. Ensuring
the window was clean before placing
the phone in the StarSense dock ﬁ xed
the issue. That's something to be aware
of with different phone models.

Using the StarSense Explorer was a
lot of fun. I live only a short distance
from the border of the biggest city in
New Hampshire, so my skies aren't
particularly dark - I can just make
out the band of the Milky Way on the
best nights. I often limit my backyard
observing with small refractors to
the Moon, casual glimpses of planets, double stars, and the rare bright
planetary nebulae. But when using the
StarSense Explorer DX 102AZ, I was
pleasantly surprised by just how many
galaxies, star clusters, and planetary
nebulae are actually visible with a small
scope aided by this trouble-free app.
This encouraged me to observe far more
than I usually do.
Celestron has long been a pioneer in
revolutionizing observing. Its SkySense
Explorer series is a real game-changer
for the hobby, much like Go To scopes
were not too long ago.
■ Associate Editor SEAN WALKER often
observes from his backyard in Litchfield,
New Hampshire.

X The StarSense Explorer leads the author toward Venus in this photo. The app tends to use
the brightest object visible in the sky (except
the Moon) as its calibration target.
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Sky & Telescope - August 2020

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