Sky and Telescope - November 2017 - 64

S&T Test Report

Rod Mollise had testing the Celestron
NexStar Evolution telescope (S&T: May
2017, p. 60).

Astrophotography

p The CGX saddle accepts both Losmandy- and
Vixen-style dovetail bars.
t Clearly marked keys and a straightforward menu
system make it relatively easy to master the basic
operation of the CGX with its NexStar+ hand control.

ally shift the azimuth and altitude of
the polar axis to re-center the star in
the eyepiece. I used this method for all
my astrophotography with the CGX
and found it to be very good. But I have
some advice that isn't in the manual
or given in the alignment instructions
that scroll across the hand control's
display. Your alignment star should be
near the meridian and celestial equator,
and tightening the locks on the mount's
altitude and azimuth adjustments
should be done in small steps, since
the mount is likely to move slightly in
the process, requiring tweaks to the
adjustments to keep the alignment star
centered as the locks are fully tightened.

Visual Tests
Initially I set up the CGX in my driveway and used it on a handful of nights
for visual observing with the 101-mm
refractor and 8-inch SCT. There's no
need to repeat instructions here for initializing the mount for Go To operation,
since they are clearly spelled out in the
manual, as well as (and perhaps more
importantly) on the hand control as
you work through the procedure. Sufﬁce
it to say the process is fast and easy, but
the large selection of alignment stars
available is only shown by name on the
hand control. Even novices should be
comfortable with Arcturus, Regulus,
64

N O V E M B E R 2 0 17 * S K Y & T E L E S C O P E

Vega, and the like, but other stars such
as Alsciaukat, Rukbah, and Wasat might
well leave veteran skygazers scratching
their heads. I always managed to initialize the CGX with familiar stars even
under the restricted view of the sky I
have from my driveway. Nevertheless,
having decent star charts handy, such
as those in Sky & Telescope's Pocket Sky
Atlas, is a good idea.
For visual observing the CGX proved
ﬁrst rate. The mount is solid and certainly capable of handling an 11- or
12-inch SCT. Slewing is smooth and
very quiet, and the mount responded
precisely and without backlash when I
pressed the direction keys on the hand
control. All the celestial-object databases we've come to expect with Go To
telescopes are available from the hand
control, and even the Sun is included
in the solar system listing. The handcontrol's illuminated and clearly labeled
keys, combined with scrolling instructions for the mount's various functions
and menus that are relatively straightforward, kept the learning curve for the
CGX quite reasonable.
While I didn't control the CGX for
visual observing with any external
planetarium software, including the
version of Starry Night supplied with
the mount, I expect it would be virtually identical to the positive experience

For astrophotography tests, I cobbled
together an adapter to attach the CGX
to one of the piers in my backyard
observatory. I used the software-assisted
method mentioned earlier to polar
align the mount. The result wasn't
perfect alignment, but it was more than
adequate for 10-minute exposures with
an optical system working at an image
scale of 1.4 arcseconds per pixel. Furthermore, the mount was plug-and-play
compatible with an SBIG autoguider
operating through MaxIm DL software.
The system worked so ﬂawlessly from
the outset that I never bothered reﬁning the polar alignment or training the
CGX's periodic-error correction.
This bodes well for anyone considering the CGX for portable astrophotography, since it should take as little as
15 minutes or so in a twilight sky to
get the mount sufﬁciently polar aligned
and ready for long-exposure photography. I especially like the CGX's ﬁneadjustment control on the polar-axis
elevation. It is precise and easy to operate even when the mount is fully loaded
with a telescope and counterweights
- something that's been a problem with
other mounts I've used.

Remote Observing
I can't always keep up with the features of every Go To mount available
today, but to the best of my knowledge

p This articulating mechanism on the CGX's
polar-axis adjustment provides precise control
of the mount's elevation even when it is loaded
with a heavy telescope and counterweights.

Sky and Telescope - November 2017

Table of Contents for the Digital Edition of Sky and Telescope - November 2017