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SKY HAPPENINGS

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

The Sky for August 2015
By Faylene Roth

 

Sunrise-Sunset
for August

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

DATE

SUNRISE

SUNSET

1

6:20am

8:29pm

2

6:21am

8:28pm

3

6:22am

8:27pm

4

6:22am

8:26pm

5

6:23am

8:24pm

6

6:24am

8:23pm

7

6:25am

8:22pm

8

6:26am

8:21pm

9

6:27am

8:20pm

10

6:28am

8:19pm

11

6:29am

8:18pm

12

6:30am

8:16pm

13

6:30am

8:15pm

14

6:31am

8:14pm

15

6:32am

8:12pm

16

6:33am

8:11pm

17

6:34am

8:10pm

18

6:35am

8:09pm

19

6:36am

8:07pm

20

6:37am

8:06pm

21

6:38am

8:04pm

22

6:38am

8:03pm

23

6:39am

8:02pm

24

6:40am

8:00pm

25

6:41am

7:59pm

26

6:42am

7:57pm

27

6:43am

7:56pm

28

6:44am

7:54pm

29

6:45am

7:53pm

30

6:46am

7:51pm

31

6:46am

7:50pm

The Milky Way stretches across the evening sky from Cassiopeia in the northeastern sky to Sagittarius in the southern sky. The middle weeks of August offer excellent stargazing opportunities since a waning last quarter moon, rising after midnight, gives way to the new moon followed by a nascent crescent moon that sets before midnight for several days thereafter. You can gauge the quality of darkness of the night sky—on a moonless night—by looking for all four stars that form the basket of the Little Dipper (Ursa Minor) as well as counting 13 or more stars within the square of Pegasus. If you can see these stars, you can also see the Andromeda Galaxy near Pegasus. Locate the two sweeping arcs that extend northward from the northeast corner star of the square of Pegasus. On the lower arc count two stars northward. Trace a perpendicular line upward through two faint stars. Our nearest neighboring galaxy appears as a faint blur above and to the right of the highest of the two faint stars.

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
We lose more than an hour of daylight in August. By month’s end the sun rises 27 minutes later and sets 40 minutes earlier.

MOON HAPPENINGS
August 6 – Dark evening skies until after midnight when the waning last quarter moon rises.
August 14 – Dark sky period for several days before and after the new moon (8:53am).
August 22 – Waxing first quarter moon brightens evening skies until after midnight.
August 29 – Full supermoon (12:35pm) rises at 7:52pm. Moon-earth perigee (closest position) August 30 at 9:24pm.

(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

Mars – After mid-month Mars reappears in the early morning twilight. Look for it low on the northeastern horizon at twilight. (Magnitude +1.9)

Saturn – The golden orb between Libra and Scorpius is Saturn. The Earth—in its inner orbit—has passed by Saturn over the last several months which makes Saturn appear to move backwards in retrograde motion. This western drift ends on August 2. After a few weeks in an apparent stationary position, the planet resumes its “real” eastward movement through the sky. Look for it overhead at twilight and lower in the southwestern skies at dark. (Magnitude +1.2)

Venus – Stargazers lose an “evening star” in early August and gain a “morning star” by the end of the month. Venus goes into inferior conjunction (passes between Sun and Earth) during the first part of August and re-emerges in the morning twilight during the last part of the month. (Magnitude -4.1)

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 Minor
Draco
Cygnus
Lyra
Hercules
Aquila
Ophiucus
Sagittarius

Eastward
Cassiopeia
Pegasus
Perseus
Pisces
Aquarius
Capricornus

Westward
Ursa Major
Boötes
Virgo
Libra
Scorpius


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

12/13
1-24
Perseus
(northward)
50-80
Swift, bright,
persistent trains
New moon period
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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