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SKY HAPPENINGS

Moab UT (at City Hall)
38O34’ N Latitude 109O33’ W Longitude
4048 ft - 1234 m

The Sky for December 2014
By Faylene Roth

 

Sunrise-Sunset
for December

(The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)

DATE

SUNRISE

SUNSET

1

7:17am

4:57pm

2

7:18am

4:57pm

3

7:19am

4:57pm

4

7:20am

4:57pm

5

7:21am

4:57pm

6

7:22am

4:57pm

7

7:22am

4:57pm

8

7:23am

4:57pm

9

7:24am

4:57pm

10

7:25am

4:57pm

11

7:26am

4:57pm

12

7:26am

4:57pm

13

7:27am

4:58pm

14

7:28am

4:58pm

15

7:29am

4:58pm

16

7:29am

4:58pm

17

7:30am

4:59pm

18

7:31am

4:59pm

19

7:31am

5:00pm

20

7:32am

5:00pm

21

7:32am

5:01pm

22

7:33am

5:01pm

23

7:33am

5:02pm

24

7:34am

5:02pm

25

7:34am

5:03pm

26

7:34am

5:03pm

27

7:35am

5:04pm

28

7:35am

5:05pm

29

7:35am

5:05pm

30

7:36am

5:06pm

31

7:36am

5:07pm

Cygnus the Swan stands on its head on the northwestern horizon transforming itself into the Northern Cross. Its long axis points downward through the Milky Way which runs west to east across the northern sky during early December evenings through Cassiopeia, Perseus, Auriga, eastward between Gemini and Orion, then between Canis Minor and Canis Major and beyond towards the outer edge of our galaxy. The eastern sky is studded with 0 and 1st magnitude stars: Aldebaran in Taurus, Rigel and Betelgeuse in Orion, Procyon in Canis Minor, Castor and Pollux in Gemini, and Sirius in Canis Major.

Twilight extends the period of daylight in three stages at each end of the day. Morning twilight begins with astronomical twilight—about 1-1/2 hours (nearly 2 during summer months) before sunrise—as the eastern horizon brightens. Nautical twilight continues—as the overhead sky turns blue and color returns to the surrounding landscape—for another 30-40 minutes. The final stage—civil twilight—provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset.

WINTER SOLSTICE
The solstice on December 21—at 4:03pm—launches the winter season in the northern hemisphere. At solar noon the sun appears 23.5 ̊ below the equator. The earth passes through the elliptical ends of it orbit around the sun at both the summer and winter solstices. The earth is closer to the sun on the winter solstice than on the summer solstice, but the sunlight diffusing across the northern hemisphere loses much of its heat and light intensity as it passes through the atmosphere at such a low angle. Daylength is down to 9 hours 28 minutes for several days around the winter solstice.
Earlier sunrises don’t begin until early January. Later sunsets begin early December.

MOON HAPPENINGS
December 6– Bright skies all night after the full moon (at 5:27am) rises at 5:35pm.
December 14– Dark evening skies until after midnight when the waning last quarter moon rises.
December 21–Dark sky period for several days before and after the new moon at 6:36pm.
December 28– Bright evening skies until after midnight when the waxing first quarter moon sets.
(The moon rises later each day—as little as 30 minutes to as much as one hour. Time of moonrise and moonset may also be delayed in mountainous terrain.)

VISIBLE PLANETS

Jupiter – The dominant light of the night sky this month is Jupiter. Once it rises—at Leo’s head—it remains in the sky throughout the night. Look for it after 10:30pm in early December, after 9:30pm at midmonth, and after 8:30pm at month’s end. (Magnitude -2.3).

Mars – Mars lingers in the southwestern sky about two hours after astronomical twilight darkens the western sky. After midmonth look for its red orb almost 25 ̊ above Venus. Mars moves from Sagittarius to Capricornus on December 5. (Magnitude +0.9).

Venus – After midmonth Venus reappears, this time in the evening sky. It will be difficult to see as it sets lower on the southwestern horizon each evening—about one hour after sunset—as nautical twilight fades to astronomical twilight. Venus moves into Ophiucus on December 8 and into Sagittarius on December 26. (Magnitude -3.8)

Saturn – Golden Saturn returns to the morning sky around midmonth. Look for it above the eastern horizon in faint Libra as astronomical twilight brightens the eastern sky. (Magnitude +1.4)

Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

Primary Sources: USGS; U.S. Naval Observatory; Your Sky at http://www.fourmilab.ch/yoursky/
To find out when the space shuttle and International Space Station are visible from your location, go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

MAJOR CONSTELLATIONS this MONTH


Overhead
Ursa Major
Ursa Minor
Cepheus
Cassiopeia
Perseus
Andromeda
Aries
Pisces
Cetus

Eastward
Auriga
Gemini
Canis Minor
Taurus
Orion
Canis Major

Westward
Lyra
Cygnus
Pegasus
Aquarius


MAJOR METEOR EVENTS
Shower
Peak
(December)
Range
(December)
Constellation Radiant
Rate
(/hr)
Details
Conditions
Geminids
13/14
7-17
Gemini
50-120
From
planetary debris
Quarter moon after midnight
Ursids
17-25
13-20
Ursa Minor
10
View
11pm-dawn
New moon
Best time to view any meteor event is between midnight and morning twilight when the radiant is overhead. Trace the path of any meteor backwards through the sky to reach its radiant--the region of the sky from which meteors appear to originate.

The star chart approximates the sky from astronomical twilight to midnight. As the night and month progresses, the constellations shift toward the northwest. The celestial equator is measured in hours (h). The ecliptic is measured in degrees

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5̊. Middle, ring, and little finger touching represent about 5̊. The width of a fist is about 10̊. The fist with the thumb extended at a right angle equals 15̊. The hand stretched from thumb to little finger approximates 20̊-25̊. The diameter of both the full moon and the sun spans only 0.5̊. Adjust for the size of your hand.

 
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