Sky & Telescope - January 2021 - 44

JANUARY 2021 OBSERVING
Planetary Almanac

PLANET VISIBILITY (40°N, naked-eye, approximate) Mercury: visible at dusk after the 8th *
Venus: loses altitude at dawn but remains visible throughout January * Mars: transits at dusk and
sets around 1 a.m. * Jupiter: can be seen at dusk until the 16th * Saturn: visible at dusk until the 7th.

Mercury

January Sun & Planets
Date

Jan 1

11

31

21

Sun

Venus

Mercury

1

16

31

Mars

1

Venus

16

31

Mars
Jupiter

Jupiter

Saturn
16

Uranus

Saturn

Neptune

Right Ascension

Declination

Elongation

Magnitude

Diameter

Illumination

Distance

1

18h

45.7m

-23° 01′

-

-26.8

32ƍ 32″

-

0.983

31

20h 54.0m

-17° 27′

-

-26.8

32′ 28″

-

0.985

1

19h 16.8m

-24° 23′

7° Ev

-1.0

4.8″

98%

1.390

11

20h

26.5m

-21° 12′

13° Ev

-0.9

5.3″

90%

1.264

21

21h

26.6m

-15° 51′

18° Ev

-0.8

6.4″

68%

1.050

31

21h 51.2m

-11° 04′

15° Ev

+0.7

8.6″

23%

0.783

1

17h 17.2m

-22° 25′

20° Mo

-3.9

10.7″

94%

1.560

11

18h 11.6m

-23° 11′

18° Mo

-3.9

10.5″

95%

1.594

21

19h

06.0m

-22° 46′

16° Mo

-3.9

10.3″

97%

1.624

31

19h

59.7m

-21° 11′

13° Mo

-3.9

10.1″

98%

1.650

1

1h

39.2m

+11° 14′

107° Ev

-0.2

10.4″

89%

0.899

16

2h 05.5m

+13° 54′

98° Ev

+0.1

9.0″

89%

1.038

31

2h 35.5m

+16° 34′

91° Ev

+0.4

7.9″

89%

1.182

1

20h

19.6m

-20° 05′

22° Ev

-2.0

32.9″

100%

5.994

31

20h

48.5m

-18° 22′

2° Mo

-2.0

32.5″

100%

6.070

1

20h

14.7m

-20° 14′

21° Ev

+0.6

15.2″

100%

10.900

31

20h 29.3m

-19° 27′

6° Mo

+0.6

15.2″

100%

10.961

16

2h 17.0m

+13° 15′

101° Ev

+5.7

3.6″

100%

19.565

16

23h

-5° 32′

53° Ev

+7.9

2.2″

100%

30.512

19.5m

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. is 149,597,871 kilometers, or
92,955,807 international miles.) For other dates, see skyandtelescope.org.

16

Uranus

Mars

Neptune
December
solstice

10"

Earth
Uranus

S PLANET DISKS have south up,
to match the view in many telescopes.
Blue ticks indicate the pole currently tilted
toward Earth.

Jupiter
Neptune

X ORBITS OF THE PLANETS
The curved arrows show each planet's
movement during January. The outer
planets don't change position enough in
a month to notice at this scale.

44

JANUARY 2 021 * SK Y & TELESCOPE

Mercury

March
equinox

Sun

Saturn

Venus
June
solstice

Sept.
equinox
http://www.skyandtelescope.org
Sky & Telescope - January 2021

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