Sky & Telescope - November 2020 - 68

S&T Test Report

p The Go2Nova 8407+ Hand Controller features eight lines of information on its back-illuminated LCD display, which is easily readable
day or night.

cables and their connections move with
the scope as it tracks across the sky,
preventing snags. You'll need a maleto-male barrel connector cable to access
the 12 VDC output. An included 5-amp,
110 VAC to 12 VDC adapter provides
power to the mount as well as to the
additional connected accessories.
The GEM45's Go2Nova 8407+ Go
To hand control displays 8 lines of
information about the mount status,
target object's location, and tracking.
The system's onboard database contains 212,000 objects. A small fabric
loop attached the hand control lets
you hang it from several knobs on the
mount. The Go To
alignment and other
operational elements
of the 8407+ menus
are very intuitive.
The hand paddle
also includes recordable
periodic error correction (PEC) that lets
you to record guiding
corrections during the
400-second cycle of
the right-ascension
worm gear, and then
play back the recorded
loop. Activating this
68

NOVEMBER 2 02 0 * SK Y & TELESCOPE

PEC feature signiﬁcantly reduced the
GEM45's periodic error.
Included with the mount is a small
GPS dongle. Plugging this accessory
into the iPORT automatically enters
location, date, and time as soon as the
dongle receives a GPS connection. Once
completed, you can unplug and store
the GPS for the rest of the night.
A serial cable that connects the hand
paddle to a laptop or other computer is
provided to update the Go2Nova ﬁrmware, if necessary. You can also directly
connect a PC to the mount via the USB
2.0 input socket on the base of the
mount to the right of the iPORT. Most
popular desktop planetarium programs
will recognize the mount as an ASCOM
device and control the GEM45. There's
also an optional WiFi adapter that allows
control of the mount with many Apple
or Android planetarium apps.

iPolar Alignment
Instead of a traditional polar alignment
scope in the RA axis, the GEM45 comes
with iOptron's iPolar electronic polaralignment tool permanently installed.
This internal camera looks through a
19-mm objective that produces a 13°
ﬁeld of view on screen and connects to
your computer via a USB 2.0 cable.
To operate the iPolar device, you ﬁrst
download the iPolar electronic polarscope control for PCs from iOptron's
website (a Mac version is available on
Apple's app store). The program has a
wide range of gain settings and exposure times to ensure Polaris and fainter
ﬁeld stars around the
pole are visible.
Once an image of
the polar region is on
screen, the software
recognizes the ﬁeld and
directs you to rotate
the polar axis so that
t The included GPS
dongle plugs into the
iPORT and automatically
inputs the date, time, and
location information into
the Go2Nova hand control.
It can be removed as soon
as the information appears
on the hand paddle.

p Instead of a polar-alignment bore scope,
the GEM45 includes iOptron's iPolar digital alignment system. Seen at the top is its
19-mm objective lens with the protective cap
removed. Above, the back end of the polar axis
includes the USB input to connect the iPolar
device to your PC. To the right is the USB 2.0
passthrough input port.

it can determine the exact center of the
mount's rotational axis.
You're then given a screen overlay
on the star ﬁeld consisting of a small
red dot and crosshair. Turning the
altitude and azimuth adjustments on
the GEM45 base moves the crosshair
directly over the red dot. When the dot
and crosshair get close, the view automatically shifts to a 10× magniﬁed view
to help reﬁne your alignment. When
completed, the right ascension axis
should be pointed to within 30 arcseconds of the pole.
I was initially confused when I had
clicked on the "raw" image display
option in the control software, which
displays what appears to be a blank
image of the ﬁeld. It turns out the stars
are there, and disabling raw setting
applies an automatic stretch to the
image, producing white stars against a
black sky with no gradation in between.
Alignment with iPolar takes a little
more time than using a traditional
bore scope, but it's worth the few extra

Sky & Telescope - November 2020

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