Sky & Telescope - June 2024 - 69

ALL IMAGES COURTESY OF THE AUTHOR
Sense, the mount operated normally. I
checked cables and connections but was
unable to resolve the problem, so I contacted
Celestron's tech support for help.
Celestron said the problem was
simply my old mount. My Advanced VX
is one of the first produced more than
10 years ago, and there'd been plenty
of hardware and firmware revisions in
the interim. The company loaned me
an Advanced VX mount of more recent
vintage, and as soon as I powered it on
with the StarSense connected, everything
functioned as it should. So, if
you own an older Celestron mount,
it would be wise to contact the company
before purchasing the StarSense
Autoguider to ensure it will indeed
work with your equipment.
In addition to performing automatic
Go To alignment as well as autoguiding
long-exposure images, the new StarSense
offers a high-precision pointing mode
that uses plate solving, in which the
camera images a star field and matches
star patterns to charts in its on-board
memory for high-accuracy pointing.
There's also a new and improved polaralignment
routine that also takes advantage
of this plate-solving upgrade.
Sensing the Stars
My first night with the StarSense paired
with my C8 Schmidt Cassegrain telescope
went well. The mount's hand control
asked if I wanted to do a polar alignment.
I selected Yes, and the controller
instructed me to slew the telescope to an
unobstructed area of the sky.
After confirming I had performed
that step by pressing the Enter button,
the mount began slewing east in
increments of 10° until it was pointing
about 50° from its original position.
When it stopped, the hand control
displayed the message " Adjust AZM "
for a few moments, then the screen
displayed both axes' error numbers and
a caret indicating the azimuth error.
I began moving the mount's azimuth
adjustment knobs slowly. The guider
continued to take images and update
the error numbers in near real-time.
After I got the error value as low as I
could, I pressed Enter, and the hand
graphic display to help during adjustment,
but I didn't find that to be a problem.
It was easy to align by watching
the error numbers decrease. The entire
procedure took me about 10 minutes.
With polar alignment achieved, the
The rear of the StarSense has two ports: a
USB-C receptacle for interfacing with a PC (left)
and an RJ-11 port (right) for the auxiliary cable
used to connect to your Celestron mount. The
device also includes built-in Wi-Fi.
control moved on to altitude, showing
the message " Adjust AZ " with the caret
now next to the altitude value. Following
those adjustments and hitting Enter
when I was ready, I was then offered the
opportunity to perform fine adjustments
on both axes. The manual advises
not to worry about getting under two
arcminutes from the pole, since the
difficulty of doing so won't produce
additional accuracy.
It was a welcome surprise to find
that the StarSense Autoguider doesn't
need to be aimed in the direction of the
celestial pole to achieve polar alignment,
which can be a real boon if you
don't have a clear view to the north.
With the hand controller there's no
NexStar hand control next prompted
me to perform a Go To alignment. The
camera took a shot of a star field, platesolved
the image, and moved the mount
to three additional positions. If enough
stars aren't visible in a field, the StarSense
automatically slews to another
one. I didn't encounter any problems
despite a fat gibbous Moon hanging
in the east. The StarSense zipped the
mount to four calibration fields, told me
it was done, and then asked if I wanted
to do a " Center Calibration " to improve
its pointing accuracy even more.
Because this was the first time I'd
used the new StarSense, I selected Yes.
I was asked to select a star and chose
Vega from the device's list of named
stars. When the slew stopped, Vega
was on the edge of my eyepiece field. I
centered it with the paddle's arrow buttons,
pressed the Enter and then Align
buttons on the hand control, and calibration
was complete. According to the
manual, you should do another Center
Calibration if you swap the StarSense
Autoguider onto a new telescope tube,
even if it's on the same mount.
How accurate is the Go To pointing
with the new StarSense? I selected the
globular cluster Messier 15, inserted a
The StarSense Autoguider has a 28-mm
effective-aperture objective lens with a focal
length of 120 millimeters. This produces a plate
scale of 4.98 arcseconds per pixel.
The mounting bracket that comes with
the unit replaces the finder bracket on your
Celestron SCT or EdgeHD OTA and secures in
place with two knurled thumbscrews.
sk yand tele scope .o r g * JUNE 2024 69
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Sky & Telescope - June 2024

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