Sky & Telescope - April 2025 - 69

The heart of the scope is its airspaced-triplet
objective lens featuring
Hoya FCD-100 ED glass - a material
prized for its color-correction capabilities.
The telescope I received was a
display model, and the first night out I
found the optics a bit out of alignment.
Since the scope doesn't allow collimation
adjustment, Airy Disk quickly sent me
a new objective assembly. At first, I was
a bit taken aback by the idea of having
to replace the lens, but my fears were
unfounded. The lens cell screws off easily,
allowing me to replace the objective
without difficulty. Star testing showed
the new objective to be in collimation.
Airy Disk provides analyses of each
scope they ship, which is unusual in an
instrument at this price. However, the
documentation proved a bit confusing.
One report showed an overall Strehl
ratio of 0.976, which is surprisingly
good for a scope at this price. A second,
more detailed report was also provided
but gave a Strehl of 0.894 instead. I'm
not sure how to account for the different
values.
Visual Performance
After replacing the objective lens, I
spent a few days with the scope evaluating
its visual capabilities. Bright stars in
the middle of the field showed no color
to my eye, and the views of the Sun
with a Herschel wedge displayed crisp
details in sunspots and granules across
the solar disk. I also tried the scope with
a Daystar Quantum Chromosphere filter
and found the background did show
a bit of haze. The appearance of a black
background when solar observing is a
very high bar to attain in scopes that
aren't designed specifically for that kind
of work. I've seen few scopes that could
achieve this feat.
Views of the Moon were contrasty
and sharp, with the lunar disk surrounded
by black sky and a few stars. I
used the bright limb as a critical color
test and only at high power could I just
catch some hints of red/yellow/orange
against the dark of space. So far so good.
Next, I performed a star test, which
revealed a small amount of spherical
aberration. During my visual tests
Left: The scope includes two ring baffles to reduce internal reflections. A threaded
aluminum lens cap protects the objective when not in use. Right: The heavy duty, 2-inch
dual-speed focuser has a bracket for mounting a finderscope or guidescope, though
neither are provided. The focuser and its 2-to-1¼-inch adapter use non-marring brass
compression rings to secure eyepieces and star diagonals.
Left: The rack-and-pinion focuser rides along three linear bearings that produce excellent
rigidity. Right: a knurled thumbscrew located on the bottom of the gearbox locks the
focuser in place.
Left: The focuser's 2-inch adapter unscrews to reveal M63 threads that accept the
company's optimal focal reducers (right).
sk yand tele scope .o r g * APRIL 2025 69

http://skyandtelescope.org

Sky & Telescope - April 2025

Table of Contents for the Digital Edition of Sky & Telescope - April 2025

Contents
Sky & Telescope - April 2025 - Cover1
Sky & Telescope - April 2025 - Cover2
Sky & Telescope - April 2025 - 1
Sky & Telescope - April 2025 - Contents
Sky & Telescope - April 2025 - 3
Sky & Telescope - April 2025 - 4
Sky & Telescope - April 2025 - 5
Sky & Telescope - April 2025 - 6
Sky & Telescope - April 2025 - 7
Sky & Telescope - April 2025 - 8
Sky & Telescope - April 2025 - 9
Sky & Telescope - April 2025 - 10
Sky & Telescope - April 2025 - 11
Sky & Telescope - April 2025 - 12
Sky & Telescope - April 2025 - 13
Sky & Telescope - April 2025 - 14
Sky & Telescope - April 2025 - 15
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Sky & Telescope - April 2025 - 17
Sky & Telescope - April 2025 - 18
Sky & Telescope - April 2025 - 19
Sky & Telescope - April 2025 - 20
Sky & Telescope - April 2025 - 21
Sky & Telescope - April 2025 - 22
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Sky & Telescope - April 2025 - 24
Sky & Telescope - April 2025 - 25
Sky & Telescope - April 2025 - 26
Sky & Telescope - April 2025 - 27
Sky & Telescope - April 2025 - 28
Sky & Telescope - April 2025 - 29
Sky & Telescope - April 2025 - 30
Sky & Telescope - April 2025 - 31
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Sky & Telescope - April 2025 - 33
Sky & Telescope - April 2025 - 34
Sky & Telescope - April 2025 - 35
Sky & Telescope - April 2025 - 36
Sky & Telescope - April 2025 - 37
Sky & Telescope - April 2025 - 38
Sky & Telescope - April 2025 - 39
Sky & Telescope - April 2025 - 40
Sky & Telescope - April 2025 - 41
Sky & Telescope - April 2025 - 42
Sky & Telescope - April 2025 - 43
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Sky & Telescope - April 2025 - 45
Sky & Telescope - April 2025 - 46
Sky & Telescope - April 2025 - 47
Sky & Telescope - April 2025 - 48
Sky & Telescope - April 2025 - 49
Sky & Telescope - April 2025 - 50
Sky & Telescope - April 2025 - 51
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Sky & Telescope - April 2025 - 54
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Sky & Telescope - April 2025 - 66
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Sky & Telescope - April 2025 - 84
Sky & Telescope - April 2025 - Cover3
Sky & Telescope - April 2025 - Cover4
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