Sky & Telescope - August 2024 - 73

120 APO accommodates the accessory
is a great feature in its favor, though
swapping out the tube segments is a
little inconvenient. Also, threading the
focuser back onto the shortened tube
results in it ending up rotated some
90° compared to when it's installed on
the full-length tube. The focuser itself
doesn't have a rotation mechanism, so
re-orienting the focus knobs requires
turning the entire tube within the tube
rings. Generally, I think you have to
decide in advance if you're going to have
a " binoviewer night " and configure the
scope accordingly.
Photographic Performance
Without either of the optional flattener
lenses, the 120 APO presents a field that
is flat over just a 20-mm image circle,
to be expected for an f/7 refractor.
However, the 1.0× Flattener and 0.8×
Reducer do their jobs very well. The 1.0×
Flattener retains the scope's native 840mm
focal length at f/7, while the 0.8×
Reducer yields 670 mm at f/5.6.
When either flattener was employed,
I saw no sign of false-color halos on
bright stars. Stars appeared sharp out to
the corners of a full-frame sensor, with
only the Reducer showing slight offaxis
aberrations. I saw no evidence of
de-centered or tilted optics; all corners
looked the same. Vignetting was hardly
noticeable with the 1.0× Flattener and
minimal with the 0.8× Reducer.
The field flatness was as good as I've
seen in many years of testing apochromats,
which almost always show some
residual coma, astigmatism, or lateral
chromatic aberration at the corners,
even when used with their companion
flatteners. With the 120 APO, you
really have to pixel-peep to see any
corner aberrations.
My only complaints with the two
flatteners are that their adapter rings
can bind, and that a camera ends up in
a different orientation when switching
The field of view with the 0.8× Reducer
is 3° by 2° with a full-frame (36- by 24-mm)
sensor. A corner blow-up shows a level of
astigmatism so slight it may not be obvious on
the printed page. The reducer is smaller than
the flattener and weighs 750 grams.
This crop shows the level of vignetting at the
corners in images of Vega taken in twilight and
with no flat-field correction applied. The 1.0×
Flattener (left) shows very little corner darkening;
the 0.8× Reducer (right) has only slight
falloff at the extreme corners.
between them. However, at only $199
each, the flatteners are a bargain and
are both worth having for the photographic
options they offer.
In short, I was impressed. As with its
visual performance, I soon chose the 120
APO for a lot of my deep-sky imaging.
Recommendations
Anyone looking to upgrade from or
supplement a 60- to 80-mm class apo
would do well to consider the 120 APO.
(An upgrade from a 100-mm scope
won't offer so great a difference.)
However, the lighter and more affordable
120 APO provides sufficient aperture
for fine planetary views, and a focal
length suitable for capturing smaller
deep-sky targets. The scope's relatively
light weight makes it easy to carry out
to the backyard and permits use with
a smaller, more portable mount. Aging
backs will appreciate that!
I can certainly recommend the Askar
120 APO. Apart from my minor complaints
about the mechanics, I found
no serious catches. I feel the scope is a
terrific bargain for both visual observers
and astrophotographers. Just be prepared
to buy some strap wrenches
to loosen its components!
¢ Contributing Editor ALAN
DYER is co-author with
the late Terence Dickinson
of The Backyard Astronomer's
Guide. He can be
reached through his website,
amazingsky.com.
sk yand tele scope .o r g * AUGUST 2024 73
http://www.amazingsky.com https://skyandtelescope.org/
Sky & Telescope - August 2024

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