Sky & Telescope - February 2023 - 70

S&T Test Report
After roughly pointing the mount
north, you begin recording short exposures
through the iPolar camera with its
iPolar control software (for PC computers
only). The software then matches the
star patterns with its internal database
of known stellar positions in a process
called plate solving. It quickly determines
the rotational center of the RA
axis within the iPolar's camera image
(marked with a " + " sign) and the true
pole's position designated with a red
circle. You then adjust the mount's azimuth
and altitude knobs. The onscreen
view zooms in as you close in on the
celestial pole, permitting finer adjustments
until you're within 30 arcseconds
of your target. Once you've moved the
" + " sign onto the circle, it turns green
and you're done.
Once set up and polar aligned, the
mount is a joy to use. The Go2Nova
Unlike a typical German equatorial mount,
the HEM27EC doesn't come with a counterweight
and counterweight shaft. It's capable
of carrying a fairly heavy telescope without
either, though there is the option to purchase a
bar for $45 that threads onto the bottom of the
declination axis.
Android devices and available on their
respective marketplaces. There's also a
USB port that allows direct computer
connection and control of the mount
with desktop planetarium programs.
Like other iOptron mounts, the
hand controller's menu is easy to
navigate, and the whir when the mount
slews to its destination is barely audible.
I controlled the mount with its hand
paddle as well as using the Sky Safari
Pro app on my iPad, connecting with
the onboard Wi-Fi. The company also
provides its own control app, iOptron
Commander Lite for both iOS and
HEM27EC includes passthrough ports
for power and USB 2.0 on the saddle
plate. I took advantage of both ports to
control and power my ZWO cameras.
The excellent Go To accuracy of the
system meant I didn't use the finderscopes
on any of the scopes I used
during my tests. Targets always landed
within the field of view after every slew.
I only needed to make fine adjustments
with the hand control to finesse the
final composition of my image.
The tracking accuracy of the
HEM27EC is excellent, even without
counterweights or autoguiding. Images
with a 71-mm f/4.9 refractor coupled to
a full-frame DSLR were effortless for the
HEM27EC, tracking 1-minute exposures
perfectly. On a different night, I tried
a 4-inch refractor operating at a focal
length of 700 mm, which also produced
round stars in most exposures. Out of 60
two-minute exposures, 41 were perfectly
tracked, and the other 19 displayed only
slightly elongated stars.
The mount managed with heavier
This photo of IC 1805, the Heart Nebula, consists of
22 unguided 5-minute exposures recorded with the
8-inch Celestron Rowe-Ackermann Schmidt Astrograph
telescope and ZWO camera seen on page 68.
70 FEBRUARY 2023 * SKY & TELESCOPE
loads, too. My 8-inch Celestron RASA
and ZWO ASI2600MC Pro camera
together weigh 9.9 kg. This combination
on the mount resulted in a total of
48 perfectly tracked 1-minute exposures
out of 60, operating at a focal
length of 400 mm. A similarly heavy
8-inch f/8 Ritchey-Chrétien scope with
the same ZWO camera also produced
many acceptable unguided exposures
at 1,625 mm, or 0.59 arcseconds per
pixel. Of the 78 1-minute test exposures
taken with this combination, 49
had round stars.
Unguided imaging is a big test for
any mount, and this one passed hand
Sky & Telescope - February 2023

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