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NIGHT SKY HAPPENINGS

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

The Sky for September 2017
By Faylene Roth

 

Sunrise-Sunset
for September

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

DATE

SUNRISE

SUNSET

1

6:48am

7:48pm

2

6:49am

7:46pm

3

6:50am

7:45pm

4

6:50am

7:43pm

5

6:51am

7:42pm

6

6:52am

7:40pm

7

6”53am

7:38pm

8

6:54am

7:37pm

9

6:55am

7:35pm

10

6:56am

7:34pm

11

6:57am

7:32pm

12

6:57am

7:31pm

13

6:58am

7:29pm

14

6:59am

7:27pm

15

7:00am

7:26pm

16

7:01am

7:24pm

17

7:02am

7:23pm

18

7:03am

7:21pm

19

7:04am

7:19pm

20

7:04am

7:18pm

21

7:05am

7:16pm

22*

7:06am

7:15pm

23

7:07am

7:13pm

24

7:08am

7:11pm

25

7:09am

7:10pm

26

7:10am

7:08pm

27

7:11am

7:07pm

28

7:12am

7:05pm

29

7:13am

7:04pm

30

7:13am

7:02pm

*Equinox 2:02pm

Ursa Major (Big Dipper) continues to scoop low towards the northern horizon, but the arc of the Dipper’s handle is high enough to direct your view westward towards Boötes. Cepheus, king to Cassiopeia, the queen, is easy to pick out overhead when facing north. Look for a typically drawn childhood house—box with steeply pitched roof—but inverted with the pointed roof directed northward. The trapezoidal body of Hercules hangs high in the western sky halfway between red-orange Arcturus (Boötes) and bright overhead star Vega. The Summer Triangle frames the overhead sky: Deneb (Cygnus) and Vega (Lyra) forming an east-west line with the apex of the triangle marked by Altair (Aquila) on the celestial equator about 40 ̊ south. The ecliptic (apparent path of the sun across the sky) dips below the celestial equator in the southwestern sky. Follow its line from the head of Scorpius eastward above Sagittarius, onward through Capricornus and the top of Aquarius. The ecliptic then crosses the celestial equator about 7 ̊ east of the head of Pisces which is where the Sun appears at the spring equinox in March. On the September 22 autumnal equinox the Sun appears to cross the celestial equator in Virgo very near the location Jupiter has occupied in our western sky over the last six months.  Pegasus (flying horse) dominates the eastern sky. The Great Square which forms its body directs our view perpendicular to the plane of our galaxy into the universe beyond.

.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.

VISIBLE PLANETS
Evening (Before Midnight)
Jupiter – Visible low on the western horizon in Virgo during the first week in September. (Magnitude -1.7)

Saturn – While officially in faint Ophiucus, it is easier to locate Saturn a short distance west of the teapot shape of Sagittarius. Saturn competes with surrounding stars for brightness, but its steady golden glow differentiates it from the sparkling stars surrounding it. It sets below the horizon before midnight. (Magnitude +1.4))

Morning (At Twilight)
Venus – Our brightest planet pierces the eastern sky about one-half hour before astronomical twilight brightens the horizon. Venus begins the month in Cancer. As it rises later each morning, it moves into Leo’s mane at midmonth. By month’s end, Venus mingles with the rear legs of Leo, trailed by Mars. (Magnitude -3.9)

Mars – The small red disk of Mars sticks with Leo throughout the month. It rises earlier each morning, but remains very low on the horizon. By month’s end Venus has descended to hover only 3 ̊ above Mars, although both will be less than 10 ̊ above the horizon which will make them difficult to see without a high vantage point. (Magnitude +1.8)

Mercury – Early risers might locate Mercury midmonth a few degrees west of Mars, but both will be only a few degrees above the horizon. (Magnitude -0.8)

MOON HAPPENINGS
September 6 – Full moon (1:03pm) rises at 8:12pm.
September 13 – Dark evening skies return with the waning last quarter moon rising after midnight.
September 20 – New moon (11:30am) yields dark skies for several nights.
September 28 – Waxing first quarter moon lights the evening sky then sets soon after midnight.

(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.)

Twilight is often the best time to look for Venus and Mercury because they frequently rise or set within one-half to one hour of sunrise or sunset. Twilight transitions between night and day in three stages at each end of the day. Morning twilight begins with astronomical twilight as the eastern horizon brightens —about 1-1/2 hours (nearly 2 during summer months) before sunrise when the sun is 18 ̊ below the horizon. Nautical twilight takes over for another 30-40 minutes—as the sun passes 12 ̊ below the horizon and the overhead sky turns blue and color returns to the surrounding landscape. The final stage—civil twilight—begins when the sun ascends to 6 ̊ below the horizon and provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset. Civil twilight covers the period after sunset during which daytime light quality persists for about one-half hour. Color then fades from the landscape during the 30-40 minute period of nautical twilight during which the overhead sky darkens while the western sky retains color. Astronomical twilight then transitions to night skies that are now darkened along the horizon.

MAJOR METEOR EVENTS
Shower
Peak
(Sept)
Range(Sept)
Constellation
Radiant
Rate
(hr)
Details
Conditions
Sporadic
None
1-30
Random
10-20
Sporadic meteors originate from interplanetary debris
Often produce

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.

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.

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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