Sky & Telescope - January 2023 - 66

S&T Test Report
to aid with leveling. The tripod's height
is okay for most Newtonian reflector
scopes and seated observers using
Cassegrains, but it's a bit short for
modest-length refractors such as the
one pictured on page 64, since the
eyepiece is low to the ground when
observing at high altitudes.
The Mark III's mounting saddle
accepts both Vixen- and Losmandystyle
dovetail bars, and as implied above
there's no need for the 5-kg counterweight
for scopes weighing less than
22 kg, thanks to the high torque of
the strain-wave drives. But the counterweight
does reduce vibration damping
times, especially for setups that
approach the weight limit.
Hand Control
The Mark III's hand control is significantly
different than ones I've used
before, but if you plan on running the
mount with a computer, the only time
you'll have to deal with the hand control
is during its required setup, which
needs to be done just once since the
hand control has a very good batterypowered
internal clock that maintains
the time, and site information (latitude
and longitude) are stored in its
permanent memory.
As with other hand controls that
lack a numeric keypad, setting information
requires scrolling. But here's where
the Mark III is different. Rather than
 Left: The Mark III's hand control,
AC power supply, and voltage
booster all have rather short
cables less than a meter in
length. As such, care is needed
when holding the hand control
to avoid accidentally pulling the
power cable out of its socket.
Because the mount runs on 24volt
DC power, it comes with the
booster for use in the field, where
observers typically use 12-volt
batteries. Right: The author evaluated
the Mark III's performance
as an astrophotography platform
using this setup, with the mount
attached to a pier in his backyard
observatory.
selecting each digit of
a value to be entered
and scrolling through
the numbers 0 to 9,
you scroll through the
whole value. For example,
setting the time
on other hand controls
without a number keypad
typically involves
selecting six digits
(two for hours, two for
minutes, and two for
seconds) and setting
each with a separate
scrolling procedure. With the Mark III,
however, you scroll through the whole
six-digit displayed time at once. A quick
click of the forward or reverse buttons
changes the seconds, while a longer
click starts the seconds flying by and
the minutes changing. Longer still and
the minutes and seconds fly as the hour
value changes. The high-speed scrolling
makes it easy to overshoot your
mark even with the fastest hand-eye
coordination, so you'll then have to
start scrolling in the reverse direction.
Nevertheless, once you get the hang of
it, you can zero in on your target value
quickly and maybe even a bit faster
than if you had to scroll through each
digit entry separately.
While it will be a moot point for
those controlling the Mark III with
planetarium software, accessing the
A machined tab on the
back of the hand control
slips into slots on the tripod
leg braces to create a
convenient, out-of-the-way
place to store the hand
control, especially when
controlling the mount via an
external computer.
numerous object
catalogs contained
in the hand control's
database also involves
scrolling, which can
be a bit tedious for
the larger catalogs. The bright-star
catalog is also a bit different in that
it steps through the included stars (in
magnitude order) of each constellation
organized in alphabetical order. Thus,
to select Rigel you scroll through the
constellations until you reach Orion
and then scroll to Rigel. You'll need
to know beforehand the three-letter
abbreviation for your star's constellation
as well as the star designation,
which will be displayed by its Greek
letter and often also common name.
It's a fine way to list the stars, but it's
also different from hand controls I've
used before.
With my growing enthusiasm for
double-star observing, I was pleased to
find the Mark III's star catalogs included
separate listings for selected STF doubles
discovered by Friedrich Georg Wilhelm
66 JANUARY 2023 * SKY & TELESCOPE
Sky & Telescope - January 2023

Table of Contents for the Digital Edition of Sky & Telescope - January 2023
