SKY HAPPENINGS
Moab
UT (at City Hall)
38O34’ N Latitude 109O33’ W Longitude
4048 ft - 1234 m |
The Sky for August 2012
By Faylene
Roth
DAYLENGTH
The period between sunrise and sunset decreases by 66 minutes in August. By month’s end, the sun rises 27 minutes later and sets 39 minutes earlier. Twilight progresses in three stages. Civil twilight lasts about one-half hour after sunset. Nautical twilight continues for another 30-45 minutes with color and shapes still apparent. Astronomical twilight begins when color and detail disappear from the surrounding view. The lingering summer twilight continues to push back the best time for stargazing until after 10:00pm through midmonth. By the end of the month, the skies are truly dark by 9:30pm. The reverse progression applies to dawn.
DATE |
SUNRISE |
SUNSET |
1 |
6:20am |
8:28pm |
2 |
6:21am |
8:27pm |
3 |
6:22am |
8:26pm |
4 |
6:23am |
8:25pm |
5 |
6:24am |
8:24pm |
6 |
6:25am |
8:23pm |
7 |
6:26am |
8:21pm |
8 |
6:27am |
8:20pm |
9 |
6:28am |
8:19pm |
10 |
6:28am |
8:18pm |
11 |
6:29am |
8:17pm |
12 |
6:30am |
8:15pm |
13 |
6:31am |
8:14pm |
14 |
6:32am |
8:13pm |
15 |
6:33am |
8:12pm |
16 |
6:34am |
8:10pm |
17 |
6:35am |
8:09pm |
18 |
6:36am |
8:08pm |
19 |
6:36am |
8:06pm |
20 |
6:37am |
8:05pm |
21 |
6:38am |
8:03pm |
22 |
6:39am |
8:02pm |
23 |
6:40am |
8:01pm |
24 |
6:41am |
7:59pm |
25 |
6:42am |
7:58pm |
26 |
6:43am |
7:56pm |
27 |
6:44am |
7:55pm |
28 |
6:44am |
7:53pm |
29 |
6:45am |
7:52pm |
30 |
6:46am |
7:50pm |
31 |
6:47am |
7:49pm |
MOON HAPPENINGS
Aug 1 – Full Moon occurs at 9:27pm and rises at 8:01pm.
Aug 9 – Last Quarter Moon rises soon after midnight.
Aug 17 – New Moon occurs at 9:54am..
Aug 24 – First Quarter Moon sets soon after midnight.
Aug 31 – Full Moon occurs at 7:58am and rises at 7:38pm
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)
BLUE MOON
Two full moons occur in August. Most of us refer to the second full moon in a month as a blue moon. The phrase “blue moon” has been used for hundreds of years to refer to rare, absurd, or unlikely events. What blue moon has come to mean in reference to the full moon, however, portrays a fuzzy history. It provides an example of the value of original reference sources.
A typical year has 12 full moons, three full moons for each of the four seasons. Occasionally, a fourth full moon in a season occurs because the moon’s orbit of 29-1/2 days is shorter than most calendar months. Each month’s full moon has a name which often refers to religious observances. In the past, when a fourth full moon occurred, there was no assigned name for it until the late 19th century when an astronomer from the Maine Farmers Almanac applied the term blue moon to the third of the four moons within the season.
In the 1940s a columnist for Sky and Telescope magazine cited the blue moon reference from the Maine Almanac but did not explain the nuance of the third of four full moons. A later author mistook the reference to a blue moon in the S&T article to refer to any second full moon within a month. That provided the basis for current use of the term blue moon on radio programs, in children’s books, and even in the game Trivial Pursuits.
METEOR EVENTS
One of the best meteor events of the year occurs throughout the first three weeks of August. The Perseid Meteor Shower peaks August 12/13 but viewing will be good August 11-14. A waning crescent moon rises several hours after midnight, so start scanning the northeastern sky around midnight. Viewing improves as Perseus, the radiant constellation, rises towards the meridian. Find Perseus by following the Milky Way northward through Cassiopeia. Perseus is the next constellation to rise in the east. This shower can produce up to 60 meteors per hour at its peak.
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.
MAJOR
CONSTELLATIONS this MONTH |
Overhead
Aquila
Cygnus
Hercules
Lyra
|
Northward
Cassiopeia
Cepheus
Draco
Ursa Major
Ursa Minor
|
Eastward
Andromeda
Aquarius
Pegasus
Perseus
|
Southward
Capricornus
Ophiucus
Sagittarius
Scorpius |
Westward
Bootes
Corona Borealis
Libra
Virgo
|
The Milky Way appears directly overhead earmarked by the three bright stars of the Summer Triangle: Vega (Lyra) west, Deneb (Cygnus) east, and Altair (Aquila) south. The small trapezoid west of Vega outlines the body of Hercules; the large square to the east of Deneb describes the body of Pegasus.
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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