Sky & Telescope - December 2020 - 44

DECEMBER 2020 OBSERVING
Planetary Almanac

PLANET VISIBILITY (40°N, naked-eye, approximate) Mercury: hidden in the Sun's glare all
month * Venus: is the leading light at dawn * Mars: transits the meridian in the early evening and sets
in the predawn * Jupiter: visible at dusk all month * Saturn: visible at dusk, sets in the early evening.

Mercury

Dec 1

21

11

December Sun & Planets

31

Date

Venus

1

Declination

Elongation

Magnitude

Diameter

Illumination

Distance

1

16h

29.0m

-21° 47′

-

-26.8

32′ 26″

-

0.986

31

18h

41.2m

-23° 06′

-

-26.8

32′ 32″

-

0.983

1

15h

45.3m

-19° 16′

11° Mo

-0.8

4.9″

96%

1.366

11

16h 50.5m

-23° 04′

5° Mo

-1.0

4.7″

99%

1.436

21

17h 59.0m

-24° 57′

2° Ev

-1.3

4.6″

100%

1.446

31

19h 09.7m

-24° 34′

7° Ev

-1.0

4.8″

98%

1.398

1

14h

38.1m

-13° 41′

28° Mo

-3.9

11.7″

89%

1.431

11

15h 27.4m

-17° 22′

25° Mo

-3.9

11.3″

91%

1.477

21

16h 18.8m

-20° 18′

23° Mo

-3.9

11.0″

92%

1.518

31

17h 11.9m

-22° 16′

21° Mo

-3.9

10.7″

94%

1.556

1

1h

01.9m

+6° 33′

128° Ev

-1.1

14.6″

92%

0.642

16

1h

16.4m

+8° 36′

117° Ev

-0.7

12.3″

90%

0.759

31

1h

37.6m

+11° 04′

107° Ev

-0.3

10.5″

89%

0.889

1

19h 51.8m

-21° 26′

47° Ev

-2.0

34.4″

100%

5.729

31

20h 18.6m

-20° 08′

23° Ev

-2.0

32.9″

100%

5.988

1

20h

01.2m

-20° 53′

49° Ev

+0.6

15.7″

100%

10.609

31

20h

14.2m

-20° 16′

22° Ev

+0.6

15.3″

100%

10.894

Uranus

16

2h

18.5m

+13° 21′

133° Ev

+5.7

3.7″

100%

19.095

Neptune

16

23h 17.4m

-5° 46′

84° Ev

+7.9

2.3″

100%

30.018

Sun

16

Mercury

31

Right Ascension

Mars

Venus
1

16

31

Jupiter

Mars

Jupiter

16
Saturn

Saturn
16
Uranus

Neptune

The table above gives each object's right ascension and declination (equinox 2000.0) at 0h Universal Time on selected dates,
and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and equatorial diameter.
(Saturn's ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet's disk illuminated by the Sun and
the distance from Earth in astronomical units. (Based on the mean Earth-Sun distance, 1 a.u. equals 149,597,871 kilometers, or
92,955,807 international miles.) For other timely information about the planets, visit skyandtelescope.org.

PLANET DISKS have south up, to match the
view in many telescopes. Blue ticks indicate the
pole currently tilted toward Earth.
+40° 16 h
HERCULES

12h

14h

10 h

+30°

Regulus

8

+10°

EC

VIRGO

LIP

TIC

Venus

25

CANCER
Betelgeuse

11
Spica

Uranus

E Q U AT O R

ER I D A N US
CANIS
MAJOR

Antares

8 am

6 am

PE GASUS

Mars

TA U R U S

Mercury

SCORPIUS
- 40°
10 am

ARIES

Rigel

Sirius

CORVUS
H Y D R A

-30°

+40°
Vega
+30°

CYGNUS
Pleiades

ORION
LIBRA

20 h

22h
ASCENSION

PISCES

Procyon

0°
-10°

0h
RIGHT

2h

4h

5

LEO

Arcturus

+20°

6h

8h

GEMINI
Dec
Castor
29 - 30
Pollux

BOÖTES

DECLINATION

10"

4 am

2 am

Midnight

+20°
+10°
0°

Neptune A Q UA R I US

21

A Q UI LA

Saturn

CETUS

Jupiter

-10°

18
CA PR I CO R N US
Fomalhaut

LOCAL TIME OF TRANSIT
10 pm
8 pm
6 pm

4 pm

SAGITTARIUS

2 pm

-30°
-40°

The Sun and planets are positioned for mid-December; the colored arrows show the motion of each during the month. The Moon is plotted for evening dates in the Americas when it's waxing (right
side illuminated) or full, and for morning dates when it's waning (left side). "Local time of transit" tells when (in Local Mean Time) objects cross the meridian - that is, when they appear due south and
at their highest - at mid-month. Transits occur an hour later on the 1st, and an hour earlier at month's end.

44

DECEMBER 2 02 0 * SK Y & TELESCOPE
http://www.skyandtelescope.org
Sky & Telescope - December 2020

Table of Contents for the Digital Edition of Sky & Telescope - December 2020
