Sky & Telescope - May 2021 - 49

Eve
E
Ev
Evening
ven
enin
iing
ng of
of May
Ma
Ma
ay
y 26
26

n

ts

wh

ing

ing

gp

um

enu

br a

mb
ra

of Scorpius, roughly midway between
the compact globular cluster M80 and
the 2.6-magnitude double star Graffias,
Beta (β) Scorpii.
While viewing the eclipse, be alert
for starlike flashes of light resulting
from meteoroid impacts on the Moon's
surface. A number of amateurs spotted
an impact flash near the lunar limb, less
than half a minute into totality during

Capturing
Mercury

apparent size and phase), the planet
is still just 7″ across and requires high
magnification to examine. Unfortunately, that requirement runs headlong
into a second problem. Even under ideal
circumstances Mercury never strays
more than 28° from the Sun. Forever
low at dusk or dawn, it's often severely
affected by atmospheric turbulence and
dispersion. Many observers simply give
up and move on.
However, there are ways to get
around these limitations. First, try
observing the planet in the daytime
when it's positioned much higher in
the sky. Second, employ orange or red
eyepiece filters to steady the image
and improve contrast. Since Mercury
lies east of the Sun during this apparition, it's well placed from late morning
through late afternoon.
To locate the planet during daylight,
you can use a Go To scope (aligned the
previous night) or the tried-and-true
method of using setting circles on an
equatorial mount to offset from the

nte

eav

vin

tota

ile l

lea

ile e

dur

wh

ile

br
m
nu
pe
ing
ra
b
nter
um
ile e
wh
ing
r
e
lip s
l ec

ets

ets

ets

wh

go. Along the East Coast of the U.S.,
only the early penumbral phase will
be visible. Observers in the Midwest
will see about half the lunar disk in
the umbral shadow before the Moon
sets at sunrise. From Los Angeles, the
Moon exits the umbra while it's still
a comfortable 14° above the horizon
around the start of dawn. During the
eclipse, the Moon beams from the head

THIS MONTH MERCURY has its best
evening apparition of the year for
observers at mid-northern latitudes.
Although the planet is brighter at the
start of May, its greatest elongation
occurs on the 17th when it stands about
11° above the west-northwestern horizon 45 minutes after sunset. Through a
telescope Mercury's phase changes from
a waning gibbous early in May, to a thin
crescent by month's end.
Despite being the only planet other
than Mars (and Earth, obviously) with
a visible surface, seeing anything more
than Mercury's phase has always posed
a challenge. One reason is that the little
planet's disk is never larger than 12.9″,
and that happens only when it's a very
thin crescent - not exactly an ideal
phase for surface studies. At 50% illumination (a good compromise between

se

ns

ns

ns

ets

Mid-eclipse
lipse
e
nith
at zenith

oo

oo

oo

oo

ns

Entire
eclipse
visible

M

M
oo

M

a

M

br

M

a

oo
nr
ise
sw
Mo
hile
on
l e av
r
i
ses
ing
Mo
wh
on
pe
ile
nu
rise
l
e
m
sd
avi
urin
ng
Mo
g
um
on
t
o
tal
rise
Mo
e c br
sw
lip
on
h il e
se
rise
ent
sw
erin
hile
gu
ent
mb
eri
ra
ng
pe
nu
m

a

M

br

ECLIPSE M A P: LE A H TISCIONE / S&T; SOURCE: USNO;
MERCURY AT DAWN: BOB K ING

the January 21,
2019, eclipse. If
you have a video
camera, consider
dedicating a second telescope to
recording potential impacts.
A lunar eclipse
is a wonderful,
slow-moving
event that anyone
can enjoy with or
a
without optical aid. Sunlight
refracted by
the atmosphere
around the circumference of Earth
bathes the deep partial and total phases
in coppers, yellows, and reds. Some
sunlight also passes through the ozone
layer in the upper stratosphere. Ozone
absorbs red light and colors the outermost, fuzzy fringe of the umbra blue.
Use binoculars or a telescope a few
minutes before and after totality to see
this feature best.

Morning
Morni
Morn
Mo
Mornin
M
orrn
rni
rnin
ning
n
nin
ing
iin
ng of
of Ma
May
May
ay 2
26
6

S TWILIGHT DELIGHTS A thin lunar crescent
paired up with Mercury at dawn in October
2015. Mercury puts in an excellent appearance
at dusk during the first three weeks of May. On
the 13th it's joined by the two-day-old Moon
in a delicate conjunction low in the northwest
during evening twilight.

Sun's position. Look up the Sun's right
ascension and declination using the
table on page 44, or by consulting a
computer program. Do the same for
Mercury. Then, attach a safe solar filter
at the objective end of your telescope
and focus on the solar disk. Adjust
s k y a n d t e l e s c o p e . o r g * M AY 2 0 2 1

49


http://www.skyandtelescope.org

Sky & Telescope - May 2021

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

Contents
Sky & Telescope - May 2021 - Cover1
Sky & Telescope - May 2021 - Cover2
Sky & Telescope - May 2021 - 1
Sky & Telescope - May 2021 - Contents
Sky & Telescope - May 2021 - 3
Sky & Telescope - May 2021 - 4
Sky & Telescope - May 2021 - 5
Sky & Telescope - May 2021 - 6
Sky & Telescope - May 2021 - 7
Sky & Telescope - May 2021 - 8
Sky & Telescope - May 2021 - 9
Sky & Telescope - May 2021 - 10
Sky & Telescope - May 2021 - 11
Sky & Telescope - May 2021 - 12
Sky & Telescope - May 2021 - 13
Sky & Telescope - May 2021 - 14
Sky & Telescope - May 2021 - 15
Sky & Telescope - May 2021 - 16
Sky & Telescope - May 2021 - 17
Sky & Telescope - May 2021 - 18
Sky & Telescope - May 2021 - 19
Sky & Telescope - May 2021 - 20
Sky & Telescope - May 2021 - 21
Sky & Telescope - May 2021 - 22
Sky & Telescope - May 2021 - 23
Sky & Telescope - May 2021 - 24
Sky & Telescope - May 2021 - 25
Sky & Telescope - May 2021 - 26
Sky & Telescope - May 2021 - 27
Sky & Telescope - May 2021 - 28
Sky & Telescope - May 2021 - 29
Sky & Telescope - May 2021 - 30
Sky & Telescope - May 2021 - 31
Sky & Telescope - May 2021 - 32
Sky & Telescope - May 2021 - 33
Sky & Telescope - May 2021 - 34
Sky & Telescope - May 2021 - 35
Sky & Telescope - May 2021 - 36
Sky & Telescope - May 2021 - 37
Sky & Telescope - May 2021 - 38
Sky & Telescope - May 2021 - 39
Sky & Telescope - May 2021 - 40
Sky & Telescope - May 2021 - 41
Sky & Telescope - May 2021 - 42
Sky & Telescope - May 2021 - 43
Sky & Telescope - May 2021 - 44
Sky & Telescope - May 2021 - 45
Sky & Telescope - May 2021 - 46
Sky & Telescope - May 2021 - 47
Sky & Telescope - May 2021 - 48
Sky & Telescope - May 2021 - 49
Sky & Telescope - May 2021 - 50
Sky & Telescope - May 2021 - 51
Sky & Telescope - May 2021 - 52
Sky & Telescope - May 2021 - 53
Sky & Telescope - May 2021 - 54
Sky & Telescope - May 2021 - 55
Sky & Telescope - May 2021 - 56
Sky & Telescope - May 2021 - 57
Sky & Telescope - May 2021 - 58
Sky & Telescope - May 2021 - 59
Sky & Telescope - May 2021 - 60
Sky & Telescope - May 2021 - 61
Sky & Telescope - May 2021 - 62
Sky & Telescope - May 2021 - 63
Sky & Telescope - May 2021 - 64
Sky & Telescope - May 2021 - 65
Sky & Telescope - May 2021 - 66
Sky & Telescope - May 2021 - 67
Sky & Telescope - May 2021 - 68
Sky & Telescope - May 2021 - 69
Sky & Telescope - May 2021 - 70
Sky & Telescope - May 2021 - 71
Sky & Telescope - May 2021 - 72
Sky & Telescope - May 2021 - 73
Sky & Telescope - May 2021 - 74
Sky & Telescope - May 2021 - 75
Sky & Telescope - May 2021 - 76
Sky & Telescope - May 2021 - 77
Sky & Telescope - May 2021 - 78
Sky & Telescope - May 2021 - 79
Sky & Telescope - May 2021 - 80
Sky & Telescope - May 2021 - 81
Sky & Telescope - May 2021 - 82
Sky & Telescope - May 2021 - 83
Sky & Telescope - May 2021 - 84
Sky & Telescope - May 2021 - Cover3
Sky & Telescope - May 2021 - Cover4
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