Sky & Telescope - March 2023 - 68
S&T Test Report by Richard S. Wright, Jr.
Altair Astro's Herschel Wedge
Here's a white-light solar filter that works just as well with a camera as it does with an eyepiece.
IT'S A GOOD TIME to be an observer
of the Sun. Not only is the solar cycle
ramping up, but North American
observers will be treated to two solar
eclipses visible across the continent
during the next 13 months. It's also a
good time to take stock of your Sunobserving
gear and to think about
any upgrades you have in mind before
inventories possibly run low. This is why
the Altair Imaging Ready 2-inch Solar
Herschel Wedge V2 caught my eye.
I've been using front-mounted,
white-light solar filters for more than
two decades, and while assembling my
observing gear recently, I became curious
to see how the views they produce
compare to a device inserted farther
down the light path behind the telescope's
objective lens.
Altair Imaging Ready
2-inch Solar Herschel
Wedge V2
U.S. Price: $359
altairastro.com
What We Like
High-contrast views of
sunspots
Integrated variable
polarizing filter
What We Don't Like
Camera rotates when
adjusting polarizing filter
How It Works
A Herschel wedge is a specially made
white-light prism for use with refracting
telescopes. (They are not recommended
for use with reflectors because of the
potential for concentrated, unfiltered
sunlight damaging internal components.)
First proposed by John Herschel
in the 1830s, the design functions like
a specialized star diagonal. Instead of a
simple mirror or 90° prism, a Herschel
wedge incorporates a trapezoidal prism
that diverts a small percentage of the
Sun's light to the eyepiece while passing
the rest through the prism where it
won't pose a threat to your vision. There
are two caveats to the design that make
it more complex than a full-aperture
tAltair Imaging Ready 2-inch Solar Herschel
Wedge V2 is a white-light solar filter that
works like a drop-in replacement for your star
diagonal.
The Altair Solar Wedge 2 comes in a custom,
hard-shell carrying case with foam inserts. It
ships with a 2-to-1¼-inch eyepiece adapter
and a 1¼-inch neutral density filter.
68 MARCH 2023 * SKY & TELESCOPE
filter. The first issue is that the light
directed towards the eyepiece is still
too powerful to be safe for viewing, so
it must be additionally attenuated. The
other issue has to do with the excess
light and heat diverted through the
rear of the prism - this needs to be
safely dispersed so that it doesn't burn
anything (or anyone) who contacts the
exiting beam. The Altair Imaging Ready
2-inch Solar Herschel Wedge V2 does
both, and does them very well.
The Altair Solar Wedge 2 is billed as
" imaging ready " for several reasons.
The first is its 2-inch-format, 46-mm
clear aperture that provides a wide,
unvignetted field that will illuminate
a full-frame detector. Additionally,
a 2-inch, circular polarizing filter is
mounted at the base of the eyepiece
turret, permitting you to quickly adjust
the brightness of the view by turning
the turret. This lets you quickly
switch between levels comfortable for
visual observing and brighter levels
for imaging, when extremely short
exposures are desirable. This setting
can be locked with a thumbscrew,
though I found it firm enough that
I didn't need to lock it. The eyepiece
turret, and the included 2-to-1¼-inch
ALL PHOTOS COURTESY OF AUTHOR
http://www.altairastro.com
Sky & Telescope - March 2023
Table of Contents for the Digital Edition of Sky & Telescope - March 2023
Contents
Sky & Telescope - March 2023 - Cover1
Sky & Telescope - March 2023 - Cover2
Sky & Telescope - March 2023 - 1
Sky & Telescope - March 2023 - Contents
Sky & Telescope - March 2023 - 3
Sky & Telescope - March 2023 - 4
Sky & Telescope - March 2023 - 5
Sky & Telescope - March 2023 - 6
Sky & Telescope - March 2023 - 7
Sky & Telescope - March 2023 - 8
Sky & Telescope - March 2023 - 9
Sky & Telescope - March 2023 - 10
Sky & Telescope - March 2023 - 11
Sky & Telescope - March 2023 - 12
Sky & Telescope - March 2023 - 13
Sky & Telescope - March 2023 - 14
Sky & Telescope - March 2023 - 15
Sky & Telescope - March 2023 - 16
Sky & Telescope - March 2023 - 17
Sky & Telescope - March 2023 - 18
Sky & Telescope - March 2023 - 19
Sky & Telescope - March 2023 - 20
Sky & Telescope - March 2023 - 21
Sky & Telescope - March 2023 - 22
Sky & Telescope - March 2023 - 23
Sky & Telescope - March 2023 - 24
Sky & Telescope - March 2023 - 25
Sky & Telescope - March 2023 - 26
Sky & Telescope - March 2023 - 27
Sky & Telescope - March 2023 - 28
Sky & Telescope - March 2023 - 29
Sky & Telescope - March 2023 - 30
Sky & Telescope - March 2023 - 31
Sky & Telescope - March 2023 - 32
Sky & Telescope - March 2023 - 33
Sky & Telescope - March 2023 - 34
Sky & Telescope - March 2023 - 35
Sky & Telescope - March 2023 - 36
Sky & Telescope - March 2023 - 37
Sky & Telescope - March 2023 - 38
Sky & Telescope - March 2023 - 39
Sky & Telescope - March 2023 - 40
Sky & Telescope - March 2023 - 41
Sky & Telescope - March 2023 - 42
Sky & Telescope - March 2023 - 43
Sky & Telescope - March 2023 - 44
Sky & Telescope - March 2023 - 45
Sky & Telescope - March 2023 - 46
Sky & Telescope - March 2023 - 47
Sky & Telescope - March 2023 - 48
Sky & Telescope - March 2023 - 49
Sky & Telescope - March 2023 - 50
Sky & Telescope - March 2023 - 51
Sky & Telescope - March 2023 - 52
Sky & Telescope - March 2023 - 53
Sky & Telescope - March 2023 - 54
Sky & Telescope - March 2023 - 55
Sky & Telescope - March 2023 - 56
Sky & Telescope - March 2023 - 57
Sky & Telescope - March 2023 - 58
Sky & Telescope - March 2023 - 59
Sky & Telescope - March 2023 - 60
Sky & Telescope - March 2023 - 61
Sky & Telescope - March 2023 - 62
Sky & Telescope - March 2023 - 63
Sky & Telescope - March 2023 - 64
Sky & Telescope - March 2023 - 65
Sky & Telescope - March 2023 - 66
Sky & Telescope - March 2023 - 67
Sky & Telescope - March 2023 - 68
Sky & Telescope - March 2023 - 69
Sky & Telescope - March 2023 - 70
Sky & Telescope - March 2023 - 71
Sky & Telescope - March 2023 - 72
Sky & Telescope - March 2023 - 73
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Sky & Telescope - March 2023 - 81
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Sky & Telescope - March 2023 - Cover3
Sky & Telescope - March 2023 - Cover4
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