Sky & Telescope - February 2024 - 69

such as a guidescope or a ride-along
imaging computer.
The scope comes in a lockable,
hard-sided case with form-fitting highdensity
foam inside. The case accommodates
the tube assembly very well,
though there isn't much additional
space for accessories.
Weighing in at 5.9 kilograms (13
The AT115EDT's triplet f/7 objective is hard to
see when viewed straight on - a testament to
the effectiveness of its antireflection coatings.
for me to see reflections when looking
directly at the objective lens. The lens
cell is nonadjustable, though I didn't see
any need to tweak its collimation.
The dew shield has no locking screw
to secure its position, but it takes a
rather strong pull to extend it, and it
remains firmly in place in all positions.
An aluminum lens cap protects the
objective when not in use.
The telescope includes a pair of
114-mm hinged tube rings with
large, knurled knobs and attached to
a 20-cm-long, Vixen-style dovetail
mounting bar. The rings are lined
with white felt, and each has three
M6-threaded holes on its flat top surfaces,
allowing users to add a second
dovetail bar for additional accessories
pounds) including rings and dovetail
bar, the AT115EDT is predictably heftier
than the smaller 4-inch apo I've owned
for several years. A medium-capacity
mount should be the rule for this
scope. It worked well on my Losmandy
G11 mount as well as on an iOptron
HAE29EC strain-wave mount. It was
a bit undermounted on my iOptron
CEM25P mount but was okay for visual
use. Like many triplet refractors, the
objective contributes much of the telescope's
weight, making the tube slightly
front-heavy. I found its balance point
to be about 25 cm from the front of the
objective cell.
While a finder isn't included with
the AT115EDT, a universal mounting
base comes affixed to the scope's
focuser. The focuser can be rotated
360° to orient a diagonal or camera to
any desired position and is locked in
place with a single thumbscrew. Likewise,
no star diagonal is included.
While many budget refractors
This Astro-Tech
optional dedicated
0.8× Photo Reducer/
Flattener screws
onto the 63-mm
male threads on the
focuser drawtube.
come with a
barely adequate focuser that owners
often replace with a better model, the
AT115EDT's stock focuser is particularly
good for both visual observing and
imaging needs. The 2.5-inch, dual-speed
unit's drawtube has 90 mm of travel
driven by a helical rack-and-pinion gear.
Two hex-head screws allow adjusting
the tension, though it didn't require any
finessing on my part. It easily supported
my 2 kg of imaging gear consisting of a
ZWO ASI2600M camera, a filter wheel,
the scope's dedicated focal reducer, and
an off-axis guider, even when the scope
was aimed near the zenith. A threaded,
2-inch adapter is also provided with
three locking thumbscrews set 120°
apart pressing on an internal compression
ring.
With the focuser of the AT115EDT
racked all the way in, the focal plane
lies 24 cm beyond the flange of the
2-inch adapter, leaving plenty of space
for accessories such as an off-axis
guider, filter wheels, field flatteners, and
focal reducers.
The focuser has a 2.5-inch-aperture drawtube with 90 mm of travel
and a printed scale on the outside. Its dual-speed focuser includes
two course-adjustment knobs and one gold anodized, 10× reduction
fine-focus knob. A 2-inch adapter threads into the end of the drawtube
with 63-mm threads. Although a finder isn't included, the scope has a
mounting base that accepts universal finder brackets. The entire focuser
is rotated by loosening the silver thumbscrew and turning the unit.
Helical rack-and-pinion gears drive the focus movement and could
support all the author's heavy imaging gear even when aimed toward
the zenith. The 2-inch adapter uses a compression ring to ensure a solid
purchase on accessories, though it may inadvertently tip some in the
optical path (see the accompanying text for details). Threaded holes on
the underside of the focuser allowed for easy installation of a ZWO EAF
focus motor bracket.
sk yand tele scope .o r g * FEBRUARY 2024 69
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