My first Magazine Sky & Telescope - 04.2019 | Page 46

APRIL 2019 OBSERVING
Planetary Almanac
PLANET VISIBILITY Mercury: lost in the solar glare all month • Venus: visible at dawn all
month • Mars: visible at dusk, sets mid-evening • Jupiter: rises near midnight, visible until dawn •
Saturn: rises early morning, visible until dawn
Mercury
21
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April Sun & Planets
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Date Right Ascension Declination Elongation Magnitude Diameter Illumination Distance
1 0 h 39.4 m +4° 15′ — –26.8 32′ 01″ — 0.999
30 2 h 26.9 m +14° 32′ — –26.8 31′ 46″ — 1.007
10.2 m –5° 36′ 24° Mo +0.8 9.4″ 29% 0.718
11 23 h 37.2 m –4° 36′ 28° Mo +0.3 7.8″ 47% 0.858
21 0 h 21.0 m –0° 40′ 26° Mo 0.0 6.7″ 61% 1.005
30 1 h 10.3 m +4° 42′ 21° Mo –0.3 5.9″ 74% 1.136
32.4 m –10° 10′ 35° Mo –3.9 13.1″ 81% 1.274
11 23 h 18.0 m –5° 54′ 33° Mo –3.9 12.5″ 84% 1.334
21 0 h 02.9 m –1° 21′ 30° Mo –3.9 12.0″ 86% 1.391
30 0 h 43.2 m +2° 51′ 28° Mo –3.8 11.6″ 88% 1.440
1 3 h 51.4 m +21° 06′ 50° Ev +1.4 4.6″ 94% 2.020
16 4 h 33.3 m +22° 58′ 45° Ev +1.5 4.4″ 95% 2.133
30 5 h 12.9 m +24° 04′ 40° Ev +1.6 4.2″ 96% 2.232
33.7 m –22° 40′ 107° Mo –2.2 39.8″ 99% 4.947
17 h 31.8 m –22° 39′ 136° Mo –2.4 43.4″ 100% 4.547
24.5 m –21° 36′ 81° Mo +0.6 16.4″ 100% 10.161
30 19 h 27.4 m –21° 31′ 109° Mo +0.5 17.2″ 100% 9.683
Uranus 16 1 h 59.5 m +11° 40′ 6° Ev +5.9 3.4″ 100% 20.847
Neptune 16 23 h 14.9 m –5° 54′ 38° Mo +7.9 2.2″ 100% 30.720
Venus
Sun
Mercury
30
16
1
Mars
1
16
30
Jupiter
Venus
16
Jupiter
h
1
Saturn
30
Saturn
Uranus
Neptune
The table above gives each object’s right ascension and declination (equinox 2000.0) at 0 h 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"
PLANET DISKS have south up, to match the
view in many telescopes. Blue ticks indicate the
pole currently tilted toward Earth.
22 h
20 h
h
1
16
0 h
h
1
Mars
+40°
h
1
18 h
16 h
14 h
12 h
RIGHT ASCENSION
Vega
+30°
+20°
10 h
LEO
Arcturus
HERCULES
PEGASUS
PISCES
0°
OPHIUCHUS
Neptune
Mercury
12
AQUILA
Venus
30
LIBRA
27
CETUS
Fomalhaut
CAPRICORNUS
24 Jupiter
Saturn
ECL
8 am
6 am
4 am
2 am
+20°
April 9
TAURUS
Uranus
0°
Sirius
CORVUS
+30°
Pleiades
Procyon
EQUATOR
CANCER
–10°
Rigel
ERIDANUS
HYDRA
CANIS
MAJOR
SCORPIUS
SAGITTARIUS
10 am
IP
Mars
Betelgeuse
April
18 – 19
TIC
+40°
ORION
VIRGO
–10°
– 40°
14
4 h
ARIES
GEMINI
Regulus
AQUARIUS
–30°
6 h AURIGA
Castor
Pollux
BOÖTES
CYGNUS
+10°
–20°
8 h
LOCAL TIME OF TRANSIT
Midnight
10 pm
8 pm
6 pm
4 pm
Apr 1
–30°
2 pm
The Sun and planets are positioned for mid-April; 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.
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A PR I L 2 019 • SK Y & TELESCOPE
–20°
– 40°