Sky and Telescope - September 2017 - 44

SEPTEMBER 2017 OBSERVING
Planetary Almanac

PLANET VISIBILITY: Mercury: Visible approximately Sept. 6 to 26, dawn, low or very low east
Venus: All September, dawn, east * Mars: All month, dawn, very low to low east * Jupiter: All month,
dusk, low to very low WNW * Saturn: All month, evening, south to SW.

Mercury

September Sun & Planets
Sept 1

11

30

21

Date

Venus

Sun

Mercury
1

16

30

Mars

1

16

30

Venus

Jupiter

Mars

16

Jupiter

Saturn

Saturn
16

Uranus

Uranus

Neptune

Right Ascension

Elongation

Magnitude

Diameter

Illumination

+8º 23′

-

-26.8

31′ 42″

-

1.009

-2º 42′

-

-26.8

31′ 56″

-

1.001

+8º 50′

9º Mo

+3.3

10.0″

6%

0.675

+11º 22′

18º Mo

-0.2

7.5″

40%

0.897

+8º 01′

14º Mo

-1.1

5.8″

81%

1.166

+1º 44′

7º Mo

-1.3

5.1″

97%

1.331

8h 36.5m

+18º 40′

32º Mo

-3.9

12.4″

84%

1.343

11

9h 25.5m

+15º 44′

29º Mo

-3.9

11.9″

86%

1.398

21

10h 13.3m

+12º 03′

27º Mo

-3.9

11.5″

89%

1.449

30

10h

55.3m

+8º 14′

25º Mo

-3.9

11.2″

91%

1.491

1

9h

58.3m

+13º 37′

12º Mo

+1.8

3.6″

100%

2.635

16

10h

34.7m

+10º 13′

17º Mo

+1.8

3.6″

99%

2.602

30

11h

07.9m

+6º 51′

21º Mo

+1.8

3.7″

99%

2.557

1

13h

22.1m

-7º 28′

43º Ev

-1.7

32.1″

100%

6.138

30

13h 43.7m

-9º 37′

21º Ev

-1.7

31.0″

100%

6.369

1

17h 21.0m

-21º 58′ 102º Ev

+0.4

17.0″

100%

9.796

30

17h 25.2m

-22º 07′

+0.5

16.2″

100%

10.272

1

10h

40.6m

30

12h

24.9m

1

10h

02.4m

11

10h

10.0m

21

11h

02.2m

30

12h

01.7m

1

Declination

75º Ev

Distance

16

1h

43.2m

+10º 02′ 146º Mo

+5.7

3.7″

100%

19.077

16

22h

56.2m

-7º 49′ 169º Ev

+7.8

2.4″

100%

28.959

Neptune
10"

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

+40°

10 h

8h
Castor
Pollux

+30°

LEO

GEMINI

6h

Mars

13

Procyon

10

EQUATOR

ERIDANUS

H Y D R A
CANIS
MAJOR
10 am

8 am

Uranus

PISCES

Neptune

Rigel

6 am

14h

BOÖTES

CETUS

Sept
5- 6

10 pm

ECL

SAGITTARIUS
8 pm

24

Sept
27 Saturn

IPTIC

Jupiter

+30°
+20°
+10°

-10°

Spica

CORVUS -20°
Antares

-30°

SCORPIUS
6 pm

12h

VIRGO
LIBRA

1

Fomalhaut

LOCAL TIME OF TRANSIT
2 am
Midnight

Arcturus

OPHIUCHUS

AQUARIUS

CAPRICORNUS

4 am

16 h

HERCULES

AQUILA

Sirius

18 h
Vega

PEGASUS

TA U R U S

ORION

-40°

20 h

CYGNUS

Betelgeuse

-10°

-30°

0h
22h
RIGHT ASCENSION

ARIES

16
CANCER

-20°

2h

Pleiades

Venus

+20°

Mercury

0°

4h

DECLINATION

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.

4 pm

2 pm

-40°

The Sun and planets are positioned for mid-September; 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

S E P T E M B E R 2 0 1 7 * SK Y & TELESCOPE
http://www.skyandtelescope.com/almanac
Sky and Telescope - September 2017

Table of Contents for the Digital Edition of Sky and Telescope - September 2017
