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SKY HAPPENINGS

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

The Sky for February 2013
By Faylene Roth


DAYLENGTH

Look forward to a gain of 62 minutes of sunlight during the month of February as the sun’s position on the ecliptic rises higher each day. Usable light is extended by about 30 minutes at each end of the day when the sun is no more than six degrees below the horizon. At dusk, this period—known as civil twilight—fades into nautical twilight over the next half hour. During nautical twilight the sun is between six and 12 degrees below the horizon. Color is less visible in the landscape when the sun drops this low. The last half hour of twilight—astronomical twilight—is marked by dark skies overhead and minimal light around the horizon. The reverse progression applies to dawn.

Sunrise-Sunset
For February 2013

Day
Sunrise
Sunset

1

7:23am

5:41pm

2

7:23am

5:42pm

3

7:22am

5:43pm

4

7:21am

5:44pm

5

7:20am

5:45pm

6

7:19am

5:46pm

7

7:18am

5:48pm

8

7:17am

5:49pm

9

7:15am

5:50pm

10

7:14am

5:51pm

11

7:13am

5:52pm

12

7:12am

5:53pm

13

7:11am

5:54pm

14

7:10am

5:55pm

15

7:09am

5:57pm

16

7:07am

5:58pm

17

7:06am

5:59pm

18

7:05am

6:00pm

19

7:04am

6:01pm

20

7:02am

6:02pm

21

7:01am

6:03pm

22

7:00am

6:04pm

23

6:58am

6:05pm

24

6:57am

6:06pm

25

6:56am

6:07pm

26

6:54am

6:08pm

27

6:53am

6:09pm

28

6:51am

6:10pm

MOON HAPPENINGS
Feb 3 – Last Quarter Moon rises soon after midnight.
Feb 10 – New Moon occurs at 12:20am.
Feb 17 – First Quarter Moon sets after midnight.
Feb 25 – Full Moon occurs at 1:26pm and rises at 6:23pm.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

CHINESE NEW YEAR
The date for Chinese New Year varies depending upon the relationship between phase of the moon and the winter solstice. This year it begins February 10—the second new moon after the winter solstice.

PLANETARY CLUSTER
Even if we can’t see it, imagine that six of our seven fellow planets range across the daytime sky on February 11 between 12 noon and 5:00pm. If we could see it, Venus would appear about 15 degrees west of the sun. Clustered about 15 degrees east of the sun would be first Neptune, then Mars, then Mercury. Uranus hangs back about 50 degrees east of the cluster with Jupiter about 75 degrees beyond it. Venus assumes an overhead position at noon with Jupiter rising on the eastern horizon. At 5:00 pm Venus will have descended to the western horizon and Jupiter would be high in the eastern sky. As evening twilight progresses, only Jupiter is visible (see VISIBLE PLANETS box). Mars, Mercury, and Venus are too close to the sun to easily distinguish. Saturn has the sky to itself from about midnight to noon when Jupiter rises.

APPARENT DISTANCES IN THE SKY
Apparent distances between celestial objects are measured in degrees. The note in italics below provides a gauge for measuring these distances. You can calibrate the size of your hand with the following test. The stars of the Big Dipper span approximately 20 degrees. Castor and Pollux, the twin stars of Gemini are about 10 degrees apart. The stars in Orion’s belt are separated by about 1.35 degrees. The apparent diameter of both the sun and the moon is 0.5 degrees. The sun and moon often appear larger on the horizon than they do when directly overhead. Use a pencil or your little finger to gauge the diameter at each position to reveal the illusion. (Try this with a full moon rather than the sun so that you do not damage your eyes.)

METEOR EVENTS
Look for sporadic fireballs throughout the month—many are seen along the line of the ecliptic (see map) and others emanate from a radiant in Auriga during the first three weeks of February. They can occur at anytime but viewing from 3:00am to dawn still provides the best opportunity.

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

VISIBLE PLANETS
Jupiter – Large gaseous Jupiter dominates an already star-studded region of the winter night sky. It’s brilliant yellow light is high overhead—westward at month’s end—by the end of evening twilight. Look for it northwest of red-orange Aldebaran (Taurus). On February 18 a waxing first quarter moon appears less than one degree below Jupiter with Aldebaran less than four degrees below the moon. (Magnitude -2.7)

Saturn – Look for the ringed planet directly overhead during early morning twilight. The golden planet appears in a sparsely-populated region of the sky—to the west of faint Libra and flanked on the west by blue-white Spica (Virgo) and farther east by reddened Antares (Scorpius). Saturn rises about one hour after midnight at the beginning of February and about one hour before midnight by the end of the month. On February 3 it rises about 3.5 degrees north of a waning gibbous moon. (Magnitude +0.6)

Note: 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
Auriga
Canis Minor
Gemini
Taurus


Northward
Cassiopeia
Cepheus
Ursa Major
Ursa Minor

Eastward
Cancer
Leo

Southward
Canis Major
Orion

Westward
Andromeda
Aries
Perseus
Triangulum


Northward the Big Dipper (Ursa Major) hangs vertically on the east side of Polaris (North Star) with the two upper stars of the dipper pointing westward toward Polaris and the three stars of its handle dangling below. Southward red-hued Betelgeuse (Orion) dominates the overhead sky bounded by the six star points of the Winter Hexagon: first, bright white star Sirius (Canis Major) below and to the east of Betelgeuse, then clockwise—Procyon (C. Minor), Pollux (Gemini), Capella (Auriga), Aldebaran (Taurus), and blue-tinged Rigel (Orion). Brilliant Jupiter (west of Aldebaran) outshines them all.


Hold the star chart high above your head and match the compass directions to the direction you are facing. Adjust the star chart by orienting Ursa Major (Big Dipper) to match its position in the sky.

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.

 
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