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SKY HAPPENINGS

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

The Sky for April 2011
By Faylene Roth

 

April
Sunrise and Sunset

DATE

SUNRISE

SUNSET

1

7:03am

7:41pm

2

7:02am

7:42pm

3

7:00am

7:43pm

4

6:59am

7:44pm

5

6:57am

7:45pm

6

6:56am

7:46pm

7

6:54am

7:47pm

8

6:53am

7:48pm

9

6:51am

7:49pm

10

6:50am

7:50pm

11

6:48am

7:51pm

12

6:47am

7:52pm

13

6:45am

7:53pm

14

6:44am

7:54pm

15

6:42am

7:55pm

16

6:41am

7:56pm

17

6:40am

7:57pm

18

6:38am

7:58pm

19

6:37am

7:59pm

20

6:35am

7:59pm

21

6:34am

8:00pm

22

6:33am

8:01pm

23

6:31am

8:02pm

24

6:30am

8:03pm

25

6:29am

8:04pm

26

6:27am

8:05pm

27

6:26am

8:06pm

28

6:25am

8:07pm

29

6:24pm

8:08pm

30

6:22pm

8:09pm

DAYLENGTH
By month’s end, sunrise jump starts the day by 41 minutes and sunset lengthens it by 28 minutes. Twilight also extends the period of usable light. Civil twilight, marks the period one-half hour before sunrise and after sunset when light is adequate for most outdoor activity. Nautical twilight is the half hour before and after civil twilight. It spans the time it takes for overhead skies to become light at dawn and dark at dusk. Astronomical twilight continues another half hour during which the horizon begins to brighten at early dawn or darkens at the end of dusk. The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.

MOON HAPPENINGS
April 3 – New Moon occurs at 8:32am
April 11 – First Quarter Moon sets after midnight
April 17 – Full Moon rises at 7:58pm and becomes full at 8:44pm
April 25 – Last Quarter Moon rises after midnight
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

METEOR EVENTS
April’s meteor activity begins around April 7 in the vicinity of Draco, a circumpolar constellation. Meteors from circumpolar constellations are visible several hours before midnight. A waxing crescent moon sets early enough to provide good viewing conditions. Virgo is another good source for meteors this month. Three separate showers from Virgo span most of the month. Best viewing for these showers is between midnight and astronomical twilight. The last two weeks of April are noted for impressive fireballs most likely to occur after midnight. Many fireballs are bits of rocky debris, often large enough to reach the ground before burning up. A waning full moon could obscure all but the brightest.

The major meteor event of April comes from the Lyrid Meteor Shower. The Lyrids are active April 16-25. As many as 20 meteors per hour can be seen during its peak on April 21/22. However, a waning gibbous moon will impede viewing.

ALPENGLOW
April’s deep red alpenglow on high desert walls, alpine peaks, and high cirrus clouds more than make up for the absence of sunsets across a low western horizon. The long wavelengths of red and orange light that project high into the sky after sunset reflect off water and dust molecules in the atmosphere and intensify the vivid reds of local rocks.

LOCAL STARGAZING
Join Red Rock Astronomers for an evening of stargazing and telescope viewing at Old City Park on Sunday, April 24, at 8:45pm. Meet at the southwest corner of the park below the bandstand. Dress warmly and bring a chair or blanket if desired. A red light or flashlight wrapped in red cellophane is advised. This event is sponsored by WabiSabi and is free and open to all ages. Call 259-4743 or 210-0066 for more information.

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.

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.


VISIBLE PLANETS
Jupiter - On April 7 Jupiter emerges from behind the sun and graces the morning twilight. It won’t be visible until midmonth when it rises on the eastern horizon with Pisces about one-half hour before sunrise. Mars (fainter) hangs about three degrees above Jupiter and Venus (brighter) hangs about 10 degrees above Jupiter. (Magnitude -2.1)

Mars - Three visible planets crowd the morning sky this month. The red orb of Mars becomes visible a few days before Jupiter makes its appearance in the eastern sky. Look for Mars around the middle of April as it rises on the eastern horizon (with Pisces) about seven degrees below Venus. (Magnitude +1.2)

Saturn - The lone visible planet in the evening and night skies this month is Saturn. Saturn rises on April 1 just as the sun sets. As the month progresses , it rises earlier each night. By month’s end it appears about 45 degrees above the horizon when it becomes visible at nautical twilight. Saturn shines slightly brighter this month for two reasons. Its opposition point with Earth occurs during the first week of April. Opposition marks the point when the earth passes between the sun and an outer planet. That puts Saturn at the closest point in its orbit to Earth. The plane of Saturn’s rings are also tilted more towards Earth right now which increases the luminosity of the planet. (Magnitude +0.4)

Venus - The first of the three planets to appear in the morning twilight is Venus. It rises at the end of astronomical twilight, about one hour before sunrise. On April 30 it appears about seven degrees south of a waning crescent moon. (Magnitude -4.0)

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.

MAJOR CONSTELLATIONS this MONTH

Overhead
Cancer
Leo

Northward
Cassiopeia
Cepheus
Perseus
Ursa Major
Ursa Minor

Eastward
Bootes
Corona Borealis
Hercules
Lyra
Virgo

Southward
Corvus
Crater
Hydra

Westward
Auriga
Canis Major
Canis Minor
Gemini
Orion
Taurus

Follow the arc of the Big Dipper’s handle eastward to Arcturus, springtime’s brightest star (Bootes). Continue the arc towards the horizon to Spica (Virgo). A loop upward and back to the handle passes through Regulus (Leo).

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.

Moab sky chart April 2011

 
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