Sky & Telescope - March 2023 - 64

S&T Test Report by Dennis di Cicco
Stellarvue's SVX127D Refractor
This 127-mm f/8 telescope defines the style and performance of a premium doublet apochromat.
t Stellarvue's SVX127D is a premium instrument
that the author found superb for viewing
solar system objects and multiple stars. The
company's website offers extensive information
on the scope's mechanical specifications,
features, accessories, and user information.
dispersion and Lanthanum elements. "
It's from Stellarvue's line of what Maris
promotes as hand-crafted telescopes
with objectives manufactured and
individually tested at the company's
Auburn, California headquarters. Each
scope's objective is guaranteed to be figured
to at least a 0.99 Strehl ratio (more
about this below) and is supplied with
its Zygo test data attesting to the lens's
quality. The scope I received for review
has a 0.993 Strehl ratio.
While the mathematically complex
Stellarvue SVX127D
U.S. Price: $2,995
stellarvue.com
What We Like
Excellent optical
performance
Equally excellent
mechanical construction
Noteworthy rotating
focuser
What We Don't Like
Nothing
REFRACTORS HAVE ALWAYS held a
special place in the hearts of amateur
astronomers. I'm certainly not the only
longtime Sky & Telescope reader who
fondly remembers admiring the ads
for Unitron refractors that graced the
magazine's back cover during the 1950s,
'60s, and early '70s. Back then there
were only a few manufacturers offering
what we would now call premium
refractors. Today, however, there are
dozens. And among those at the top of
the list is California-based Stellarvue
founded by Vic Maris.
Last summer and fall I spent several
months using the Stellarvue SVX127D
that we borrowed from the company
for this review. It's a 127-mm (5-inch)
f/8 apo refractor with an air-spaced
doublet objective made with " super-low
64 MARCH 2023 * SKY & TELESCOPE
Strehl ratio for assessing telescope
optics has been around for more than a
century, it's only recently been associated
with telescopes intended for the
amateur community, complementing
the familiar " 1/4-wave " criteria commonly
cited as what's necessary for
diffraction-limited optics. A Strehl ratio
of 0.80 is considered diffraction limited,
and the higher the ratio the better the
optical performance. But what exactly
does the Strehl ratio quantify? Simply
put, it's the ratio of light collected by a
telescope objective that's focused into
the central core of a star's image (the
Airy disk) compared with that of a theoretically
perfect objective.
Expectations
Well before the SVX127D arrived on
my doorstep for testing, Stellarvue's
claimed Strehl ratio of 0.99 or better
had set the bar pretty high for the
optical performance I was expecting.
And after months of observing the Sun,
Moon, Venus, Saturn, Jupiter, and a slew
of multiple stars, I'll flat out say I was
never disappointed. There was nothALL
PHOTOS BY THE AUTHOR

http://www.stellarvue.com

Sky & Telescope - March 2023

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