Asta's Almanac, is based on Whats Up, Ron? a monthly almanac for Northern American astronomersastras

Astra's Almanac

What's Up in the Night Sky?

September 2012 - Vol. 16, No. 9

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Features: Calendar | Lunar Almanac | Monthly Topic

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Links to On-line Almanacs

Starry Trails:

Abram's Planetarium
Sky Calendar

Classical Astronomy
The Sky this Month

Angular Measurement Review: It is interesting to note that the relationship between the angle subtended by combinations of fingers on your fully outstretched arm are the same for all viewers. This is due to the fact that the hand's size is proportional to the arm's length. A shorter arm is attached to a smaller hand while a longer arm is attached to a larger hand, thus the angle measured remains the same. If you hold your arm fully outstretched, your little finger, when sighted down your arm, is one degree wide. Your three middle fingers is five degrees, your fist, 10 degrees, and the distance between your little finger and your pointer finger is 15 degrees no matter what your age or size.

The Summer Triangle asterism, Vega (Lyra), Denab (Cygnus) and Altair (Aquila), is still quite prominent overhead as darkness falls. Arcturus (Bootes) is now dipping to the NW horizon. From a dark site, the myriad stars of the Milky Way (the visible "arm" of our galaxy), "flow" eastwards through the "W" asterism of Cassiopeia and to bright Capella (Auriga) glowing in the NE. The Great Square asterism of Pegasus burns high in the SE while lonely Formalhaut (Piscis Austrinus) shines far below, very close to the horizon. "The Big Dipper" asterism (Ursa Major) is nearly horizontal and now sits low on the N horizon. In the E, Aldebaran (Taurus) shines, a sure sign of Autumn.

MERCURY will not be visible this month in the northern hemisphere. VENUS is bright in the morning sky, still in a position that favors observers in the northern hemisphere. The morning star is moving through Leo and is less than 4 degrees away from Regulus at the end of the month. JUPITER is passing through Taurus rising at midnight. MARS moves into Libra and sets in the evening. SATURN is heads into the sun and disappears in the evening twilight by month's end.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time; dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times. Unfortunately some of these events may occur during daylight hours in your area.

Mars and Saturn are 10 degrees apart. The first magnitude star Spica is still nearby. Venus 9 degrees S of Pollux.
Moon at apogee. (farthest from the Earth) Keep watching as Jupiter and the moon move through Taurus, lining up for some great views this night.
Mercury at superior conjunction
Venus 4 degrees N of the Moon
Venus 3 degrees S of the Beehive cluster (M33). The waning Moon appears below.
The Zodiacal Light or "false dawn" is visible in the E about 2 hours before sunrise. This pyramidal glow is caused by meteoroids, dust particles spawned by passing comets, etc., that have settled into the ecliptic plane (path followed by the Sun, Moon and planets), reflecting the Sun’s light before it rises here. This phenomenon will be visible until about October as long as the Moon does not interfere.
Keep watching Saturn, Mars, and Spica as they conclude the dance of the planets (and stars) this month after providing us with a fabulous show this year.
Occultation of Spica by the Moon, visible over the Indian Ocean. Saturn nearby.
Moon at perigee. Occultation of Mars occurs over South America, the red plannet is a tenth of a degree N of the lunar disk.
Equinox, day and night of equal duration at low and high latitudes, Autumn begins.
Venus 7 degrees S of the Moon.
The full Harvest Moon (closest to the Autum equinox) was traditionally used as an aid to those who reaped the harvest after the Summer growing season. Venus less than 4 degrees away from Regulus.
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Lunar Almanac for September 2012

Phases of the Moon Phase and Date(s)

Best viewed before local midnight

new moon icon


Deep Space Objects
first quarter moon icon

1st. Qtr

Planets & Moon
full moon icon


last quarter icon

Qtr 08

Deep Space & Planets

Topic of the month: Perseus and Andromeda

In the northern hemisphere as the summer gives way to autumn, sky watchers remember the story that the constellations enacted in the sky, the story of Andromeda and Perseus. This is due to the prominence of the circumpolar constellations of Cassiopeia (The Lady in the Chair) and Cepheus (The King) as they appear to rise in the eastern sky after the sun sets. The constellations of Andromeda and Persues follow behind, and are visible in the evening sky on fall nights.

In Greek mythology, Andromeda was the daughter of Cepheus and Cassiopeia, king and queen of Ethiopia. Queen Cassiopeia boasted that Andromeda was more beautiful than the Nereids, nymphs who were followers of the god of the sea, Poseidon. This made Poseidon very angry and to punish the queen for her arrogance, he sent a sea monster named Cetus to ravage the coast of Ethiopia. Because of the suffering of the people, King Cepheus consulted the oracle of Apollo, who told the king that there would be no respite unless he sacrificed his daughter, Andromeda, to the monster. The beautiful Andromeda was chained to a rock on the coast. Fortunately for Andromeda, the hero Perseus spotted her as he was flying past on his magic winged sandals. Perseus was on his way to the island of Seriphos returning his task of slaying the Gorgon, Medusa. Perseus saw the plight of Andromeda, and showed the head of the Gorgon to Cetus, turning the sea monster to stone. He set Andromeda free and the two were married. Like all characters in Greek myths, they lived far from happily ever after.

fall sky image

The prominent stars in this story light up the fall nights. The constellation Cassiopeia is also called the celestial "W" or "M" after the letters they resemble. There is a double star cluster in this modern constellation that is often referred to as the "double cluster." They are visible to the naked eye from dark sites. The Milky Way galaxy is bright in this constellation, the spiral arm extending in Perseus. The bright star Beta Persei is also known as Algol or the "Demon Star", representing the head of the Medusa. This variable star, was the first variable star of its type recognized, called an eclipsing variable. It is really a star system comprised of three stars. The brightest of these, Beta Persi A, is regularly eclipsed by the dimmer component, Beta Persei B, this causes the apparent magnitude of the star to fluctuates from 2.1 - 3.4 every two days. The eerie nature of this star was noted by the Egyptians long ago.

The constellation of Andromeda is best known today for hosting a very large galaxy, called the Andromeda galaxy. Containing over 400 billion stars, this galaxy can be seen by the naked eye from a very dark site. It appears as a large elliptical cloud when observing conditions are right. This galaxy is the largest member of our Local Group of galaxies that includes the Milky Way and another spiral galaxy in the constellation of Triangulum. These are the three major galaxies and a host of other smaller galaxies and star system belong to our Local Group.

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. The above image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Editing was done for educational purposes only. Stellarium offers much more to amateur astronomers and is being used in planetariums and to guide telescopes in the field. Simple charts like the one above can be used on the internet for non-profit, illustration purposes. Proper credit is due of course! Thank you to the makers of this fine program from Astra's Star Gate.

This installment of "Whats Up?" is ©2012 by Dawn Jenkins for Astra's Stargate. View Ron Leeseburg's Farewell Issue

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