| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Skyguide April to June 2001 April 1: At 2 a.m. on the first Sunday in April, Daylight Time begins in most of the United States. Beware jokers! Set your clocks and timers ahead one hour. Daylight Time is not observed in Arizona, Hawaii, American Samoa, Puerto Rico, the Virgin Islands, and most of Indiana. April 7: Passover. The lunar Jewish calendar uses the leap month of Adar to ensure that Passover always comes in Spring. Otherwise, as in the Islamic calendar, all holidays would shift eleven days from year to year and move around the calendar. April 8: Full Moon, known to the Algonquin by many names, including the “Pink Moon,” the “Sprouting Grass Moon,” and the “Fish Moon.” Since this is the first Full Moon of Spring, next Sunday (the 15th) will be Easter Sunday. April 23: New Moon at 8:27 a.m. Tomorrow night (the 24th), a day-old crescent Moon will be visible low in the west at sunset. The sighting of the first visible crescent after New Moon marks the start of Safar, the second month of the Islamic calendar. May 7: The Full Moon, also called the “Salmonberry Bird Moon” by the Haida, sits on the border between Libra and Scorpius. May 22: New Moon at 7:47 p.m. Tomorrow night’s sighting of the first visible crescent moon marks the beginning of Rabi’ al-Awwal, the third month of the Islamic calendar. June 5: This Full Moon is listed in some calendars on the 6th, since it occurs at 1:39 Universal Time on that date. Converting to pdt puts the moment of Full Moon at 6:39 p.m. on the 5th. June 17: Autumnal equinox ... on Mars’ Northern Hemisphere. June 21: Summer solstice for the Northern Hemisphere at 12:38 a.m., marking the start of Summer. The Sun rises and sets at its most northerly points on the horizon and attains its greatest midday height. North of the Arctic Circle, it’s above the horizon 24 hours a day; south of the Antarctic Circle, it’s below the horizon 24 hours a day. The New Moon moves between Earth and the Sun at 4:38 a.m., casting its shadow onto the surface of our planet and causing a total solar eclipse visible from southern Africa and Madagascar. The Planets Mercury On April 1st, this little planet is a morning object, already retreating into the glare of the rising sun and barely visible low in the east just before dawn. As it reappears in the evening sky in late April, the high inclination of the ecliptic makes Mercury seem to leap high above the Sun for its best evening appearance of the year in May, when it sets as much as two hours later than the Sun. Look for it next to Saturn on May 6 and next to Jupiter on May 16. After the moon passes by on the evening of May 24, Mercury plummets back down toward the Sun and disappears until late June, when it returns to the predawn sky. Venus In early April, Venus is a morning object, emerging from the glow of the rising Sun as Mercury sinks into it. Reaching its greatest western elongation on June 8, Venus rises two hours before the Sun, and then dwells in the morning sky for the rest of the year. The crescent Moon swings by on the mornings of April 20 and 21, May 19, and June 17. Mars The Red Planet rises around midnight at the beginning of April against the stars of Ophiucus and is due south just prior to dawn. This is a good time to compare Mars’ orange color with that of the nearby star Antares in Scorpius—they are often confused with one another. Mars rises slightly earlier in the southeast at sunset (see box). A medium-sized amateur astronomy telescope will reveal the planet’s disk and maybe a fleeting glimpse of a dark patch or two. The Moon passes nearby in its waning gibbous phase on the evenings of April 12 and 13, and May 10 and 11, and is full on June 5 and 6. Jupiter is prominent in the west at sunset in April, just above fainter Saturn, and gradually sinks lower into the twilight. Even with binoculars (preferably mounted on a tripod), its disk is obvious, and its four largest moons are easily visible through a telescope. In conjunction with Mercury on May 16, it disappears into the Sun’s glow in late May. The crescent Moon swings nearby on the evening of April 25, and closer yet on May 23. Saturn accompanies brighter Jupiter in the west at sunset, when it is located lower and sets first. You can glimpse its rings through a telescope until early May, when it disappears only to emerge again in the morning sky of late June. Sunrise - Local Noon - Sunset April 1 6:55 a.m. pdt 1:14 p.m. pdt 7:33 p.m. pdt May 1 6:14 a.m. pdt 1:07 p.m. pdt 8:00 p.m. pdt June 1 5:49 a.m. pdt 1:08 p.m. pdt 8:26 p.m. pdt July 1 5:52 a.m. pdt 1:14 p.m. pdt 8:36 p.m. pdt (Times are for San Francisco, CA, and are accurate to within two minutes.)
Bing F. Quock is a member of the staff of the Morrison Planetarium.bquock@calacademy.org |
Spring 2001
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