Australian Sky & Telescope — July 2017

http://www.skyandtelescope.com.au 69

of the night’s best objects if you can’t
decide on what you want to see.
The reliability of the Evolution’s
Wi-Fi connection impressed me. I could
control the telescope from as far as 20
metres away on a wide-open observing
field. The manual warns that competing
Wi-Fi signals may cause problems,
but that never happened to me. The
only time my iPhone or Android tablet
disconnected was when I let the devices
go into power-saving sleep mode. When
I woke them, SkyPortal reconnected
automatically in a few seconds.
Accurate pointing is a good thing,
but how did the objects look? The
Celestron 9.25’s 235-mm aperture,
2,350-mm focal length f/10 optics have
a reputation for excellence, and I was
certainly impressed with them. Despite
only so-so atmospheric steadiness,
the scope produced satisfying views
of Saturn. The 9.25 is a powerful
performer on the deep sky, too. From
my light-polluted backyard, its generous
aperture enabled me to resolve brighter
globular star clusters into hordes of tiny
pinpoints.
Mediocre seeing conditions
prevented me from doing a definitive
star test, but from what I could tell, the
appearance of the diffraction pattern of
a slightly out-of-focus star was similar
on both sides of focus — an indication
of well-corrected optics.
When I began observing with the
Evolution, I was concerned I might
accidentally bump the star diagonal into
the telescope base if I chose an object
too close to the zenith. Fortunately,

theSkyPortalappandthehandcontrol

both include an altitude limit that is

adjustable, and this always prevented

the diagonal from hitting the base.

In addition to its Wi-Fi capabilities,

the Evolution is different from most

other fork-mount SCTs in this aperture

range because of its single, rather than

double, fork arm. Some prospective

owners have expressed concern about

that, and I did find the Evolution mount

somewhat less stable than heavier,

double-arm forks. Nevertheless, the

Evolution is still quite useable, even

at high power. With the tripod legs

retracted, a rap on the tube produced

vibrations that took up to 4 seconds to

die out at 180×. Focusing at high power

without creating excessive vibration

is easy if you use a light touch on the

knob. The advantage of the single-arm

SLeft: Although the scope comes with Celestron’s NexStar+ hand controller, the telescope

can be completely controlled using a smartphone or tablet running the SkyPortal app. A laptop

computer can be connected to drive the telescope via a mini-USB input at the bottom of the

controller. Right: The Celestron logo on the fork arm lights up to indicate the status of the internal

battery charge. Not shown on the rear of the arm at right are two additional RJ-11 auxiliary ports,

the Wi-Fi on/off switch and a Wi-Fi reset button.

SThe base of the mount includes the charger
port, two RJ-11 auxiliary ports to attach the
hand controller or a StarSense alignment unit, a
USB power output port and the power switch.

fork is that this nearly 25-cm SCT is far

easier to transport and assemble than

similar size double-arm SCTs.

Imaging performance

Many new amateurs looking for a

telescope want to know “Can it take

pictures?” Due to its light single-

arm fork mount, this would not be

a telescope I’d choose for the most

demanding deep sky imaging, but you

can take pictures with it. It's more than

adequate for high-resolution planetary

photography, and also good enough to

let new imagers get their feet wet with

some deep sky imaging.

As a trial, I shot images of a few

bright objects at the Cassegrain focus

on the Evolution. The telescope as

delivered only works in alt-azimuth

mode, and the inherent field rotation