Sky & Telescope - February 2023 - 69

slightly more effort than for a basic
star tracker. Indeed, the compact
mount is about the same size and
weight of some star trackers. But while
most star trackers can work unguided
with focal lengths of around 135 mm
or less, the HEM27EC drive is accurate
enough for unguided imaging at much
larger image scales.
The lightweight equatorial head
attaches to the tripod by two hex-head
screws, which also lock down the
azimuth axis during polar alignment.
A hex wrench is provided that stores in
a convenient, magnetic slot just above
one of the screws. This wrench also
fits every screw on the mount and can
also be inserted into holes around the
mount's altitude adjustment wheel to
provide additional torque if needed.
Fully assembled, the mount on the
Carbon Fiber Tripod weighs just 10.4 kg.
With the tripod legs retracted and folded
in, the top-to-bottom distance of the
package is only 81 cm - easily fitting in
the back seat of most any vehicle.
Missing from the setup sequence is
installing a counterweight shaft and
weight to balance the load across the
RA axis. The mount's manual states
flatly, " No RA balance is needed for an
HEM27 mount. " The RA shaft can only
be turned when the mount is powered
up and operated by the hand controller
or a computer.
Because there's no clutch to release
the RA shaft, the telescope load and
counterweight can't be precisely balanced
even with the optional counterweights
and shaft installed. The declination
axis, however, includes a small
locking knob just below the saddle plate
to release its gear and allow balancing
the declination axis.
When attaching your telescope,
you need to take care after tightening
the lever that clamps the saddle
dovetail. Its protruding plastic handle
is spring-loaded and should be rotated
after tightening to place the lever in the
" up " position so that it won't interfere
with declination movement. This step
is important enough to be mentioned
in the user manual. My failure to check
the lever position one night resulted in it
colliding with the declination housing.
Alignment with iPolar
Once assembled, the mount needs to
be polar aligned to perform at its full
This shot of NGC 7293, the Helix Nebula,
demonstrates the capabilities of the HEM27EC.
The photo was assembled from 47 out of the
78 unguided 60-second exposures recorded
with an 8-inch f/8 Ritchey-Chrétien telescope
and ZWO ASI2600MC Pro camera.
potential. Absent on the HEM27EC is a
polar finderscope, or at least an eyepiece
for one. Instead, alignment is done
with the built-in iPolar electronic pole
finder. It's a small lens and camera that
requires the use of an external computer
to run the iPolar software. While
this wasn't as convenient or straightforward
as an optical finder, iPolar produces
dead-on polar alignment and is
worth the extra trouble.
This view of the mount shows at bottom
one of the azimuth adjustment screws, which
double as the main connection for securing
the head to the tripod. An included hex wrench
stores conveniently in a magnetic compartment
just above the azimuth locking screw.
The polar axis includes the power input and
switch, the port to connect the iPolar alignment
device, a USB 2.0 connection, an ST-4-compatible
autoguiding port, and hand controller (HBX).
A 12-volt output and USB passthrough port is
seen on the rear of the saddle plate.
This view of the iOptron HEM27EC shows
its integrated iPolar's objective lens uncovered.
Altitude and azimuth adjustment knobs are at
bottom. Small holes around the edge of the
altitude adjustment wheel accept an onboard
hex wrench to help precisely turn the wheel.
sk yand tele scope .o r g * FEBRUARY 2023 69
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Sky & Telescope - February 2023

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