Sky and Telescope - May 2018 - 44

MAY 2018 OBSERVING
Planetary Almanac

PLANET VISIBILITY: Mercury: hidden in the Sun's glow all month * Venus: visible at dusk *
Mars: rises near midnight, highest near dawn * Jupiter: visible at dusk, highest near midnight *
Saturn: rises late evening, visible until dawn

Mercury

May 1

11

May Sun & Planets

31

21
Venus

Date

Sun
1

16

31

Mercury

Mars

1

16

31

Venus

Jupiter

Mars

16

Jupiter

Saturn

Saturn
16

Uranus

Uranus

Neptune
Neptune

PLANET DISKS have south up, to match the
view in many telescopes. Blue ticks indicate the
pole currently tilted toward Earth.
2h

0h

22h

Declination

Elongation

Magnitude

Diameter

Illumination

Distance

1

2h

31.7m

+14° 55′

-

-26.8

31′ 45″

-

1.007

31

4h

30.3m

+21° 50′

-

-26.8

31′ 33″

-

1.014

1

0h

54.1m

+2° 41′

27° Mo

+0.3

7.8″

46%

0.859

11

1h 40.6m

+7° 21′

24° Mo

-0.1

6.6″

61%

1.018

21

2h 41.5m

+13° 39′

18° Mo

-0.6

5.7″

79%

1.177

31

3h 59.4m

+20° 13′

7° Mo

-1.6

5.2″

96%

1.298

1

4h

21.8m

+22° 23′

27° Ev

-3.9

11.5″

88%

1.450

11

5h

13.8m

+24° 17′

30° Ev

-3.9

11.9″

86%

1.397

21

6h

06.6m

+25° 03′

32° Ev

-3.9

12.4″

83%

1.340

31

6h 59.0m

+24° 38′

34° Ev

-3.9

13.1″

81%

1.278

1

19h 41.0m

-22° 44′

107° Mo

-0.4

11.1″

88%

0.845

16

20h

09.1m

-22° 09′

115° Mo

-0.8

12.9″

89%

0.726

31

20h

31.6m

-21° 47′

124° Mo

-1.2

15.1″

91%

0.619

1

15h

08.1m

-16° 16′

171° Mo

-2.5

44.7″

100%

4.413

31

14h 53.4m

-15° 18′

156° Ev

-2.5

44.2″

100%

4.462

1

18h 37.9m

-22° 16′

122° Mo

+0.4

17.5″

100%

9.502

31

18h 32.4m

-22° 21′

152° Mo

+0.2

18.1″

100%

9.161

16

1h

+10° 54′

25° Mo

+5.9

3.4″

100%

20.799

16

23h

-6° 25′

69° Mo

+7.9

2.3″

100%

30.291

51.5m
09.7m

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.com/almanac.

10"

+40°

Right Ascension

20h

18h

16h

14h
12h
RIGHT ASCENSION

Vega

+30°

PISCES

PEGASUS

21

Uranus

+10°

A Q UILA

-20°
-30°
- 40°

CETUS

Neptune

8

CA P RICO RNUS
Fomalhaut

May 5
Mars
SAGITTARIUS

10 am

8 am

6 am

4 am

May
28 -29
Saturn

18

TA U R U S

CANCER

+10°
Betelgeuse
Procyon

0°

Antares

E

PT
CLI

S C OR P I U S

2 am

ORION

LIBRA

Jupiter

Midnight

IC

Rigel -10°

Spica
CORVUS

Sirius

-20°

H Y D R A
CANIS
MAJOR

LOCAL TIME OF TRANSIT
10 pm
8 pm
6 pm

4 pm

-30°
2 pm

The Sun and planets are positioned for mid-May; 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

M AY 2 0 1 8 * S K Y & T E L E S C O P E

4h
+30°

Venus

EQUATOR

11
DECLINATION

-10°

24

VIRGO

A Q UA RIUS

0°

AURIGA

Regulus

OPHIUCHUS

Mercury

6h
GEMINI

LEO

Arcturus

HERCULES

8h
Castor
Pollux

BOÖTES

CYGNUS

ARIES

10h

- 40°
http://www.skyandtelescope.com/almanac
Sky and Telescope - May 2018

Table of Contents for the Digital Edition of Sky and Telescope - May 2018
