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?

May 2012 - Vol. 16, No. 5

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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:
Suzieastro

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.

As May brings the lengthening days, the hours of nightly observation decrease as well, it is always with a bit of sadness that we say good-bye to the Winter and Spring constellations, Gemini, Leo, and Virgo. The early evening presence of Archurus, the second brightest star in the northern sky, reminds us that the bright star clouds of the Milky Way will soon be brightening up those dark evenings when the Moon is small enough to allow us to truly enjoy those galactic treasures. As the evening turns to morning, the bright stars of the summer triangle follow until just before sunrise, the Milky Way is at the zenith, high overhead.

MERCURY appears in the morning skies this month, but is more favorably placed for observers located in the southern hemisphere. VENUS is fast approaching inferior conjunction and is now rapidly heading toward the Sun for the transit of the solar disk next month. (See the feature article of the 2012 transit of Venus below.) JUPITER is in conjunction with the Sun this month and will not be visible. MARS now past opposition, is receding from the Earth and dimming, but is still visible much of the night in the constellation Leo. SATURN is also past opposition this month, but will be visible most of the night. Watch Saturn and Spica this month, as well as Saturn and Mars as these two planets will less than 5 degrees apart in August. Watch how they appear the last two weeks of the month and how their positions compare with Venus.

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.

DATE EVENT
01
Mars and Regulus within 6 deg as the month opens. Keep your eye on these two! Mars will be E of Regulus by month end and 15 degrees ahead of the first magnitude star.
04
Spica and Saturn are joined by Moon, close to full.
3-6
The closest full moon of 2012, occurs when the moon reaches perigee of 221,802 miles or 356,955 km. Costal areas experience high tides!
5-6
Eta Aquarid meteor shower peak this morning will be obscured by the full moon.
6-9
The Moon at perigee this month brings some of the highest Spring tides to the coastal areas
13
Jupiter in conjunction with the Sun.
18
Venus 2 degrees W of El Nath.
19
Moon at apogee.
20
Annular Solar eclipse, unfortunately, this is not visible from most of North America.
22
Venus will appear close to the thin crescent of the young Moon for the last time as it approaches inferior conjunction and that very rare transit, that will occur on June 5. (See below)
27
Mercury at superior conjunction. (Not Visible)
31
Conjunction of Saturn, Spice and the gibbous moon.
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Lunar Almanac for May 2012

Phases of the Moon Phase and Date(s)

Best viewed before local midnight

new moon icon

New
20

Deep Space Objects
first quarter moon icon

1st. Qtr
28

Planets & Moon
full moon icon

Full
05

Moon
last quarter icon

Last
Qtr 12

Deep Space & Planets

Topic of the month: The Transit of Venus

Transits of Venus are rare events that occur once every 105.8 or 121.5 years alternately, in pairs that are separated by eight years. The last transit of Venus occurred in June 2004. A transit of Venus is a rare event, with none occurring in the 20th century. This is because Venus is 3.4 degrees off the ecliptic and rarely does our sister planet come directly between us and Sun. What a privilege it is to be able to view this rare event.

On June 5, 2012, the rare alignment of Earth, Venus, and Sun will once again occur. For observers in North America, the transit of Venus becomes visible in late afternoon and will still be in progress at sunset. Venus will appear as a black silhouette about 58-arc seconds in diameter, moving slowly across the Sun's disk. Please be extremely careful while trying to view this event. Please remember Ron's advice when view this extremely rare event: I CANNOT STRESS ENOUGH THE IMPORTANCE OF PROPER EYE PROTECTION WHEN VIEWING THE SUN! ONE SLIP AND YOU COULD SEE "SUN SPOTS" (CAUSED BY NEARLY INSTANTANEOUS EYE DAMAGE) FOR THE REST OF YOUR LIFE!!

Historically, Johannes Kepler calculated that the inner planets orbits intersect the plane of the Earth's orbit around the Sun. (The planet Mercury's orbit is inclined 7 degrees to the Earth's orbit, creating an average of 16 transits per century.) Kepler predicted transits of Venus would occur in 1631 and 1639. The first observation of the transit of Venus was made in 1639 by Jeremiah Horrocks, a young astronomer from England. Edmund Halley also encouraged astronomers who were alive during transits of Venus to make the most of the opportunity.

To learn more about the transit of Venus, check out NASA's eclipse site that contains pages on transits at: http://eclipse.gsfc.nasa.gov/transit/transit.html and http://eclipse.gsfc.nasa.gov/OH/transit12.html

Check out the transit of Venus on the internet. There are still opportunities to join tours and expeditions. I recommend the articles from Sky and Telescope and the Classical Astronomy as well. The Transit of Venus dot Org site will also lead you to more details.

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

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

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