Sunrise and Sunset Times for April 2010

DAYLENGTH
Earlier sunrises and later sunsets provide 68 minutes more of daylight this month. Twilight also extends the hours of daylight. Civil twilight occurs approximately one-half hour after sunset when you can easily function without artificial light. Nautical twilight, about one hour after sunset, may require artificial light to assist your movements. Astronomical twilight begins about one and one-half hours after sunset. A faint glow fades from the western sky over the next one-half hour. The opposite progression occurs at dawn. (The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)

MOON HAPPENINGS
April begins with a waning gibbous moon rising a little before midnight. On April 2 it appears after midnight in the SSE sky near Antares (Scorpio). The third quarter moon occurs April 6. A new moon occurs April 14. On April 15 a waxing sliver of moon pairs with Mercury just below Venus. The first quarter moon occurs April 21. On April 25 a waxing gibbous moon rises with Saturn in the eastern sky. A full moon returns on April 28. The month ends as it began with the moon rising in Scorpius a little before midnight. (The time of moonrise and moonset assumes a flat horizon. Actual time may vary depending upon the landscape.)

METEOR EVENTS
April abounds with meteor showers. During the first week a minor meteor shower has a radiant in Serpens Caput which rises about 10pm in the southern sky. It peaks the night of April 4. Another meteor shower with a radiant in the circumpolar constellation Draco is active throughout the first half of the month. Throughout the month meteors will stream from Virgo in the southern sky. The last two weeks of April are well known for the occurrence of fireballs (large meteors as bright as Venus that have the potential to reach the ground as meteorites). April fireballs can originate from any region of the sky. The third week of April will offer the best opportunity to view them because the waxing new moon will not cause much light interference. These meteor showers are a backdrop to the main event of the month. April 16-25 the Lyrids Meteor Shower graces the nighttime sky. At its peak on the night of April 21/22 this shower can produce 10-20 meteors per hour. A first quarter moon sets soon after 2am. The best time to view any meteor event is when the radiant is overhead. That is usually between midnight and 5:00am.

LOCAL STAR COUNT
I’ll be joining Red Rock Astronomers one evening this month for a tour of the night sky and telescope viewing. Look for flyers around town during the first week of April and watch for an announcement in The Ad-Vertiser. You can also call 259-4743 or 259-3313 for more information. The stargazing events are sponsored by WabiSabi and all ages are welcome.

Note: Hold your hand at arm’s length to measure apparent distances in the sky. Adjust for the size of your hand. 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 hand stretched from thumb to little finger equals 20 degrees. The diameter of both the full moon and the sun spans only 0.5 degree.

VISIBLE PLANETS
Jupiter - The dominant light in the predawn sky this month is Jupiter. It appears on the ecliptic a little south of the celestial equator about one hour before sunrise. (Magnitude -2)

Mars - Look high in the western sky for the bright red disk of Mars between the twin stars of Gemini and the sickle-shaped head of Leo. It appears in the faint constellation Cancer. Each evening Mars advances a little farther east. By April 19 it will have moved eastward through the center of Cancer. Mars is fading in brightness as its orbit recedes from Earth, but it still matches the brightness of Saturn and the first magnitude stars. (Magnitude +0.5)

Mercury - On April 8 Mercury is at its greatest eastern elongation from the sun (farthest point from the sun in its orbit). To see Mercury, first find Venus in the western sky, then use binoculars to scan to the west towards the horizon for Mercury. On April 15 use binoculars to find Mercury to the right of a thin crescent moon right below Venus in the western sky. (Magnitude +0.1)

Saturn - Look for Saturn in the faint constellation Virgo as twilight fades. Its yellow disk appears below Denebola (tail of Leo). Extend a line through Mars, Regulus (Leo’s heart) and Saturn to find Spica (Virgo). (Magnitude +0.5)

Venus - Both Venus and Mercury are in Pisces this month, but the constellation is too faint to be seen so close to the sun. Venus continues to appear low in the western sky so it may not be visible until late in the month when it can be seen between the two star clusters of the Pleiades and the Hyades (the V of Taurus). (Magnitude -3.9)
Note: 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 Cancer Leo Northward Cassiopeia Cepheus Perseus Ursa Major Ursa Minor Eastward Bootes Corona Borealis Hercules Lyra Virgo Southward Corvus Crater Hydra Westward Auriga Canis Major Canis Minor Gemini Orion Taurus The celestial equator (extension of earth’s equator upon the celestial dome) spans E to W. The ecliptic (sun’s path across the sky) runs SE to NW. The constellation overhead at midnight on the ecliptic indicates where the sun will be at noon (daylight savings time disregarded) in six months. 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 night sky from astronomical twilight to midnight. As the night and the month progress, the constellations will shift toward the northwest.