Sky & Telescope - April 2023 QR - 75
POLARIZER: GARY SERONIK; MOON FILTER: CELESTRON
reflects about 12% of the light hitting
it - about the same as an asphalt road.
So why is it so dazzling? Simply because
you're usually looking at it at night,
when it's surrounded by a dark sky and
your eyes likely have become at least
partially sensitized to the nighttime
environment through a process known
as dark adaptation. When you train your
scope at the Moon, your poor observing
eye gets blasted with more photons than
it's ready for. You might even experience
a disorienting lunar afterimage when
you look away. So, even if the view isn't
harmful, you may well find it uncomfortable.
Thankfully, taming lunar
illumination is pretty easy.
The first thing to try is boosting
your scope's magnification. This has
the effect of spreading out the Moon's
light, making it appear less brilliant.
How much power do you need for this
to work? The more you apply, the dimmer
(and larger) the Moon appears.
The obvious advantage of this approach
is that you don't have to buy anything
extra - you probably already have the
necessary eyepieces. You don't want
to go too far down this road, though.
If the image starts looking blurry due
to excessive magnification, it's time to
back off a bit.
But what if the view is still too bright
for your tastes, or you want to see the
entire lunar disk but just more dimly?
This is where filters are your friend.
You can purchase a range of specialized
filters that screw into the base of
your eyepiece - there's even one called
a " Moon filter, " and its only job is to
dim the view. Sometimes also referred
to as " neutral density filters, " they
can be purchased in a couple of different
strengths, or transmission values
(expressed as a percentage of the light
allowed through). Just be sure to pick a
model that matches the barrel diameter
of the eyepiece(s) you plan to use
- typically either 2-inch or 1¼-inch.
Expect to spend $12 to $25 for one.
A more versatile option is a variable
polarizing filter. The advantage to this filter
is that you can dial in a wide range of
transmission values. In effect, a variable
polarizer works like a dimmer control
POLARIZING POWER A variable-polarizer
eyepiece filter consists of two halves (shown
separated in the photo above) that allow the
user to adjust the brightness of the telescopic
image over a wide range. As a bonus, the two
parts of the filter can be separated and used
as a conventional polarizer filter for daytime
viewing of the first- or last-quarter Moon.
for the Moon, allowing you to fine-tune
its brightness to precisely match your
preference. Such filters also allow you to
make the Moon much dimmer than any
conventional fixed filter can. A variable
polarizer is essentially a pair of polarizers
that rotate with respect to each
other to achieve the dimming effect.
And because you are in effect buying
two filters, it tends to be more expensive
than a regular Moon filter. Typically, a
variable polarizer costs in the range of
$25-$30 for 1¼-inch models.
What I like about this solution is
that you can usually unscrew one of the
filter elements and use it as a regular
polarizer. Such a filter offers surprisingly
good daylight views of the Moon,
when it's near first- or last-quarter
phase. Used this way, the polarizer
doesn't dim the image, rather it renders
the daytime sky an appealing dark blue,
thus improving contrast.
For the sake of completeness, I'll
also mention planetary filters. These are
colored filters designed to enhance the
contrast of surface features on planets
(principally Mars and Jupiter). Since
the Moon is essentially gray, there's
minimal color contrast to work with.
Instead, these devices render the lunar
surface a specific color. (The green one
LUNAR GOODIE Dedicated Moon filters like
the one shown here are a quick and easy way
to dim the telescopic view of the lunar surface.
Also known as neutral-density filters, they're
available in several different strengths. Using
such a filter couldn't be easier. Simply thread
it into the barrel of your eyepiece and enjoy
the view.
is handy if your goal is to convince
someone that the Moon really is made
of green cheese.) Planetary filters do
cut down lunar luminance, but unless
you want a fake blue Moon (or a red,
orange, yellow, or green one), the
options already mentioned are better.
Of course, if you have some planetary
filters already, there's no harm in trying
one out to see if you like it.
Although this discussion has focused
on improving your observing comfort,
you'll also see more detail when your
eye isn't being overwhelmed with photons.
Indeed, the finest view I ever got of
ol' Luna was through a friend's homebuilt
16-inch reflector telescope. He'd
just completed figuring the mirror but
hadn't yet sent it out to have its reflective
coating applied. Eager to test this
new optic, we aimed his new scope at
the Moon. And what a view it was! The
lunar surface was rendered with the full
(and impressive) resolution of a 16-inch
aperture, but thanks to the bare glass,
it was only as bright as it would have
appeared in a 3-inch telescope. It was
an astonishing sight - richly detailed
but wonderfully comfortable.
Mind you, for a true lunaphile,
bright or dim, the Moon is always an
astonishing sight. ¢
sk yand tele scope .o r g * APRIL 2023 75
https://skyandtelescope.org/
Sky & Telescope - April 2023 QR
Table of Contents for the Digital Edition of Sky & Telescope - April 2023 QR
Contents
Sky & Telescope - April 2023 QR - Cover1
Sky & Telescope - April 2023 QR - Cover2
Sky & Telescope - April 2023 QR - 1
Sky & Telescope - April 2023 QR - Contents
Sky & Telescope - April 2023 QR - 3
Sky & Telescope - April 2023 QR - 4
Sky & Telescope - April 2023 QR - 5
Sky & Telescope - April 2023 QR - 6
Sky & Telescope - April 2023 QR - 7
Sky & Telescope - April 2023 QR - 8
Sky & Telescope - April 2023 QR - 9
Sky & Telescope - April 2023 QR - 10
Sky & Telescope - April 2023 QR - 11
Sky & Telescope - April 2023 QR - 12
Sky & Telescope - April 2023 QR - 13
Sky & Telescope - April 2023 QR - 14
Sky & Telescope - April 2023 QR - 15
Sky & Telescope - April 2023 QR - 16
Sky & Telescope - April 2023 QR - 17
Sky & Telescope - April 2023 QR - 18
Sky & Telescope - April 2023 QR - 19
Sky & Telescope - April 2023 QR - 20
Sky & Telescope - April 2023 QR - 21
Sky & Telescope - April 2023 QR - 22
Sky & Telescope - April 2023 QR - 23
Sky & Telescope - April 2023 QR - 24
Sky & Telescope - April 2023 QR - 25
Sky & Telescope - April 2023 QR - 26
Sky & Telescope - April 2023 QR - 27
Sky & Telescope - April 2023 QR - 28
Sky & Telescope - April 2023 QR - 29
Sky & Telescope - April 2023 QR - 30
Sky & Telescope - April 2023 QR - 31
Sky & Telescope - April 2023 QR - 32
Sky & Telescope - April 2023 QR - 33
Sky & Telescope - April 2023 QR - 34
Sky & Telescope - April 2023 QR - 35
Sky & Telescope - April 2023 QR - 36
Sky & Telescope - April 2023 QR - 37
Sky & Telescope - April 2023 QR - 38
Sky & Telescope - April 2023 QR - 39
Sky & Telescope - April 2023 QR - 40
Sky & Telescope - April 2023 QR - 41
Sky & Telescope - April 2023 QR - 42
Sky & Telescope - April 2023 QR - 43
Sky & Telescope - April 2023 QR - 44
Sky & Telescope - April 2023 QR - 45
Sky & Telescope - April 2023 QR - 46
Sky & Telescope - April 2023 QR - 47
Sky & Telescope - April 2023 QR - 48
Sky & Telescope - April 2023 QR - 49
Sky & Telescope - April 2023 QR - 50
Sky & Telescope - April 2023 QR - 51
Sky & Telescope - April 2023 QR - 52
Sky & Telescope - April 2023 QR - 53
Sky & Telescope - April 2023 QR - 54
Sky & Telescope - April 2023 QR - 55
Sky & Telescope - April 2023 QR - 56
Sky & Telescope - April 2023 QR - 57
Sky & Telescope - April 2023 QR - 58
Sky & Telescope - April 2023 QR - 59
Sky & Telescope - April 2023 QR - 60
Sky & Telescope - April 2023 QR - 61
Sky & Telescope - April 2023 QR - 62
Sky & Telescope - April 2023 QR - 63
Sky & Telescope - April 2023 QR - 64
Sky & Telescope - April 2023 QR - 65
Sky & Telescope - April 2023 QR - 66
Sky & Telescope - April 2023 QR - 67
Sky & Telescope - April 2023 QR - 68
Sky & Telescope - April 2023 QR - 69
Sky & Telescope - April 2023 QR - 70
Sky & Telescope - April 2023 QR - 71
Sky & Telescope - April 2023 QR - 72
Sky & Telescope - April 2023 QR - 73
Sky & Telescope - April 2023 QR - 74
Sky & Telescope - April 2023 QR - 75
Sky & Telescope - April 2023 QR - 76
Sky & Telescope - April 2023 QR - 77
Sky & Telescope - April 2023 QR - 78
Sky & Telescope - April 2023 QR - 79
Sky & Telescope - April 2023 QR - 80
Sky & Telescope - April 2023 QR - 81
Sky & Telescope - April 2023 QR - 82
Sky & Telescope - April 2023 QR - 83
Sky & Telescope - April 2023 QR - 84
Sky & Telescope - April 2023 QR - Cover3
Sky & Telescope - April 2023 QR - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com