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Last updateWed, 27 Aug 2014 10am

Astronomy

Few people will choose to arise early to catch the start of the lunar eclipse on Saturday morning, April 4, when the spring’s first full moon begins to enter the umbra, or dark central core, of Earth’s shadow at 3:16 a.m. local time.

For the next 1.7 hours, more and more of the moon will be immersed in the Earth’s circular dark shadow, until the start of the total eclipse at 4:58 a.m. Even before then, the rusty color typical of the moon in deep eclipse should be noticed—at least in the lower part of the moon’s disk, closer to the center of Earth’s shadow. Totality lasts less than five minutes, as the northern (upper) edge of the moon barely passes within the outer edge of Earth’s umbra. There should be a pronounced difference in color and brightness between the top and bottom edges of the moon.

Totality ends by 5:03 a.m., after which the moon will gradually emerge from the shadow, with the eclipse concluding at 6:45 a.m. From the Coachella Valley, the moon sets several minutes before then, cutting off our view.

If you prefer to watch this early-morning eclipse for just an hour, I recommend from 4:30 until 5:30 a.m., centering on the deepest eclipse at 5 a.m. At mid-totality, the moon will be quite dim compared to a normal full moon, and observers in dark locations will get a spectacular view of the Milky Way.

Other bright objects of April mornings: Spica will be just 10 degrees to the upper left of the moon at mid-eclipse on April 4, with golden Arcturus high to their upper right. The next morning, on Easter Sunday, April 5, Spica will appear within 4 degrees below the moon, and on April 8, the moon will appear within 2 degrees to the upper right of Saturn, and 10 degrees to the upper right of twinkling Antares, the red supergiant star marking the scorpion’s heart. The waning gibbous moon moves through the predawn Milky Way April 9-11, and by April 12, it has passed last quarter phase and appears slightly less than half full. The last easy view of the waning crescent will be low in the east an hour before sunup on April 16, with another chance for binocular users a half-hour before sunrise on April 17, only 30 hours before the new moon.

The brightest “stars” in evening mid-twilight: In order of brilliance, they are: Venus, in the west to west-northwest; Jupiter, passing just south of overhead around midmonth; Sirius, in the southwest sky, bluish and twinkling, heading lower as the month progresses; Mercury, emerging from superior conjunction beyond the sun on April 9 to appear very low in the west-northwest to lower right of Venus starting around April 18; Arcturus,in the east-northeast to east, higher as month progresses; and Capella, high in the northwest.

This is a good month to follow the motion of Venus against background stars. During April 9-11, Venus passes within three degrees south of the Pleiades, or Seven Sisters star cluster,an especially beautiful sight for binoculars! On April 16-22, Venus passes Aldebaran and the Hyades cluster, those stars together making up the “V”-shaped head of Taurus, the Bull. Meanwhile Jupiter lingers within 5-6 degrees east of the Beehive all month. Use binoculars to find that star cluster.

On April 19, 40 minutes after sunset, the thin young crescent, 32 hours past new, will be low in the west to west-northwest. Binoculars may show Mercurywithin 8 degrees to the moon’s lower right; and dim Mars within 4 degrees to the upper left of Mercury, and within 5 degrees to the lower right of the moon. This is the same night Venuspasses closest north (7 degrees to the upper right) of Aldebaran. On April 20, the lovely crescent moon will be almost directly below Venus, within 9 degrees to the lower right of Aldebaran, and 9 degrees to the lower left of the Pleiades. On April 21, the moon climbs to 5 degrees to the upper left of Aldebaran, while Venus shines within 8 degrees to their upper right. Far to their lower right, dim Mars glows only 1.5 degrees to upper left of bright Mercury.

On Apr. 22, Betelgeuse, shoulder of Orion, is 10 degrees south (to the lower left) of the crescent moon, while Mercury and Mars appear closest to each other, 1.3 degrees apart, with fainter Mars to the lower left. This is the first evening emerging Mercury is higher than sinking Mars. They’ll be 2 degrees apart on April 23, while the moon is midway between Betelgeuseand Pollux, brighter of Gemini twins. On April 24, the fat crescent moon exits the winter hexagon nearly halfway from Procyon to Pollux. On April 25, the first-quarter moon, half full, is 9 degrees to the lower right of Jupiter.

On April 26, the moon is in waxing gibbous phase, 8 degrees to Jupiter’s lower left, and on the next night, April 27, it appears 4 degrees south of Regulus, heart of Leo, the Lion.

On April 30, Mercury passes within two degrees south of the Pleiades. (Use binoculars to see the cluster low in twilight so late in April.)

Mid-April is a good time to start keeping a checklist of bright stars seen each evening. Many bright stars are gathered in the western sky, including the huge winter hexagon. Striking changes in the visibility of stars will occur in the next several weeks, as a result of the Earth’s revolution around the sun. An observer’s log can be downloaded here.

The Astronomical Society of the Desert will host a public star party on Saturday, April 25, from 8 to 10 p.m. at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74. For more information and directions, visit www.astrorx.org.

Robert Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs.

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