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SKY HAPPENINGS

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

The Sky for July 2015
By Faylene Roth

 

Sunrise-Sunset
for July

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

DATE

SUNRISE

SUNSET

1

5:58am

8:46pm

2

5:58am

8:46pm

3

5:59am

8:46pm

4

5:59am

8:46pm

5

6:00am

8:46pm

6

6:00am

8:46pm

7

6:01am

8:45pm

8

6:01am

8:45pm

9

6:02am

8:45pm

10

6:03am

8:44pm

11

6:03am

8:44pm

12

6:04am

8:43pm

13

6:05am

8:43pm

14

6:05am

8:42pm

15

6:06am

8:42pm

16

6:07am

8:41pm

17

6:07am

8:41pm

18

6:08am

8:40pm

19

6:09am

8:40pm

20

6:10am

8:39pm

21

6:11am

8:38pm

22

6:11am

8:37pm

23

6:12am

8:37pm

24

6:13am

8:36pm

25

6:14am

8:35pm

26

6:15am

8:34pm

27

6:16am

8:33pm

28

6:16am

8:33pm

29

6:17am

8:32pm

30

6:18am

8:31pm

31

6:19am

8:30pm

The Milky Way dominates the nighttime summer sky. Trace the constellations listed below in the Overhead Constellations section—from north to south—through the Milky Way. Cassiopeia lies in the direction of the outer edge of the galaxy. Follow Cepheus, Cygnus, and Aquila towards the galaxy center which lies between Sagittarius and Scorpius, about 25,000 light years away.

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.

DAYLENGTH
Rising summer temperatures make it difficult to believe that the days are getting shorter—a decrease of 41 minutes since last month’s Summer Solstice. Extended summer twilight lingers until after 10:00pm when the western horizon finally darkens.

APHELION
If shorter periods of daylight are not producing cooler days, what effect will aphelion have? The Earth reaches aphelion—its farthest point from the sun—on July 6 at 2:00pm. The 3% increase in distance (about 3,000,000 miles) since perihelion on January 4 has minimal effect on temperature. The tilt of the Earth’s axis from the plane of its orbit earns that credit by presenting the tipped face of the northern hemisphere into the direct rays of the sun’s heat. Aphelion does, however, contribute to the length of the seasons. The summer season in the northern hemisphere is about five days longer than its winter season. This happens because the speed of the Earth in its orbit slows as it moves farther from the sun.


MOON HAPPENINGS
July 1– Full moon (8:20pm) rises at 8:22pm.
July 8– Dark evening skies until after midnight when the waning last quarter moon rises.
July 15– Dark sky period for several days before and after the new moon (7:24pm).
July 23– Waxing first quarter moon brightens evening skies until after midnight.
July 31– Full moon (2:43am) rises at 8:37pm.
(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 – July evenings begin with Jupiter hovering on the western horizon about 3 ̊ above Venus. Jupiter gradually moves to the right of Venus where the two planets continue to set in tandem throughout the first half of the month. By month’s end Jupiter is setting about one-half hour ahead of Venus. (Magnitude -1.8)

Saturn – Look for the golden glow of Saturn high in sky—above red supergiant star Antares (Scorpius)— when the full moon rises on the evenings of July 1 and again on July 31. Saturn sets before morning twilight. (Magnitude +1.0)

Venus – Venus shares the western horizon with Jupiter during evening twilight this month. Watch the waxing new moon graze past Venus on the evenings of July 17-19. Jupiter appears to the right of Venus and blue main-sequence star Regulus (Leo) sits above the two planets. (Magnitude -4.2)

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
Cassiopeia
Cepheus
Cygnus
Aquila
Sagittarius
Scorpius

Eastward
Pegasus
Capricornus

Westward
Ursa Major
Boötes
Virgo
Libra


MAJOR METEOR EVENTS
Shower
Peak
(December)
Range
(December)
Constellation Radiant
Rate
(/hr)
Details
Conditions
Delta Aquarids

28/29
1-5
Aquarius
20
southward-midnight to dawn
Waxing
gibbous 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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