Sky & Telescope - February 2021 - 35

S Although the telescope's 10-inch-long dew
shield does not retract, it can be unscrewed
from the lens cell to make it easier to blow or
gently brush off any dust and tree pollen from
the objective. The metal lens cap fits on the
dew shield and offers significant protection.

Arcturus in deepening twilight that was
clearly brighter and more contrasty than
the one produced by the 6-inch. The
modern multi-coatings on the Evostar
objective likely account for much of the
difference, but the scope's three internal
light baffles offered better suppression
of scattered light than did the baffling
I used for the 6-inch. As the night wore
on, same-magnification views in both
scopes always seemed brighter and more
contrasty in the Evostar, and it wasn't
just a subtle difference.
Indeed, the only aspect of the
two scopes that was evenly matched
involved resolution. During weeks of
observing under varying seeing conditions and moonlight, there was never a
time when one scope outperformed the
other for resolving tight binary stars or
lunar and planetary details.
The Evostar always came to a crisp
focus even with magnifications between
500× and 600×. Only the slightest touch on the fine-focus knob was
enough to show the difference between
an image being in and out of focus. For
a two-element objective, the Evostar's
color correction is noteworthy. There
is only a slight hint of color fringing
around out-of-focus star images. In
focus there were no noticeable color
halos around bright stars. Spherical
aberration was also well-corrected. Stars
showed similar diffraction patterns on
both sides of focus. The only exception

occurred during autumn evenings when
the temperature was rapidly falling
and I could sometimes detect a hint of
spherical aberration in the out-of-focus
images, which is not unusual for a
refractor objective acclimating to temperature changes. Even so, it was never
enough to degrade in-focus views.
The Moon was a particularly good
target for the Evostar, especially when
the seeing permitted using high magnifications. The scope produced excellent,
high-contrast views along the lunar
terminator without a hint of scattered
light washing over the deep shadows.
And while timing of the observation
was as important as the telescope, on
the evening of last October 24th I had
one of my most memorable views of the
famed Straight Wall and the top of the
adjacent crater Birt catching the first
rays of lunar sunrise.
During the fall, Jupiter and Saturn
barely made it above the treetops as
seen from my observatory, but there
were times when I had decent views of
both and several instances when Jupiter's moon Ganymede clearly appeared
as a tiny disk rather than just a point of
light. The highlight of the season was,
of course, Mars, and here the Evostar
did not disappoint. I was able to identify
dozens of dark albedo features and the
shrinking south polar cap as I followed
the Red Planet on nights when the seeing was decent.
Overall, I was extremely pleased
with the Evostar's optical performance.
T Even with the tube rings fully tightened, the
telescope tended to slip when pointed to high
elevations. The author solved the problem by
adding several thin cork strips between the
ring's felt lining and the telescope tube.

I can't speak for everyone, but it's difficult for me to imagine anyone nitpicking the views this scope is capable of
producing. It is a very fine instrument
for serious visual observers and delivers
everything I expect from a 150-mmaperture telescope.

A Word about Mountings
Because of their length, refractors put
more demands on a telescope mounting
than instruments with compact tube
assemblies. As such, it's desirable to use a
mount rated for a greater weight capacity
than the telescope. My observing setup
with the two refractors mounted
together totaled about 60 pounds, or
slightly more than half of the rated
capacity of the Sky-Watcher EQ8-R Pro.
That might seem like overkill, but it
really was a pleasure using such a solid
platform with responsive slow-motion
controls. A mount with twice the weight
capacity of the Evostar 150 would certainly be a good choice for the scope.
If owning a high-quality, large-aperture refractor is on your bucket list, I
can highly recommend the Evostar 150
APO. Its optical performance for visual
observing is on par with some of the
fi nest refractors I've ever used, including ones costing three and four times
the price of the Evostar. The light touch
needed to operate the 2-inch focuser's
fi ne-focus knob is a real plus for
observing at high magnifications. The
focuser was also more than adequate
for all kinds of astrophotography
with cameras even as heavy as today's
typical DSLRs. The biggest advantage
that the heavy-duty focuser on the
Evostar 150DX APO brings to astrophotography is its potential for using
the optional f/6.2 focal reducer. While
that setup is a notch below the capability of Sky-Watcher's 150-mm Esprit
astrograph, it's more than enough for
a lot of serious deep-sky photography.
Needless to say, I'm impressed with the
150-mm Evostar refractor.

„ DENNIS DI CICCO spends a lot of
clear nights testing equipment from his
backyard observatory in Boston's
western suburbs.
sk yandtelescope.org * FEBRUARY 2 021

35


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Sky & Telescope - February 2021

Table of Contents for the Digital Edition of Sky & Telescope - February 2021

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Sky & Telescope - February 2021 - 1
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