| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Skyguide July to August 2003 Bing F. Quock July 3 Earth at aphelion, or farthest from the Sun, once again shows that the seasons are not caused by Earth’s distance from its star, but by the tilt of Earth’s axis and the resulting change in the angle of solar illumination. July 6 First quarter Moon against the stars of Virgo, almost due south at sunset. With the Moon illuminated from the right-hand side (as seen from the northern hemisphere), this is a good time to look with binoculars or a telescope for the shadows of craters and mountain ranges along the division between its nighttime and daytime sides. July 13 Full Moon rising an hour after sunset between Sagittarius and Capricornus the Sea-Goat. It is known to the Chinese as the “Hungry Ghost Moon,” to Celts as the “Claiming Moon,” and to the medieval English as the “Mead Moon.” July 28 New Moon at 11:52 p.m., Pacific Time (some calendars use Universal Time and list New Moon tomorrow). On the 29th, look for a beautiful, thin, 20-hour-old crescent low in the west-northwest after sunset—scan to the left of the Moon for Jupiter. August 11 Full Moon, also known as the “Fruit Moon” to the Cherokee, the “Women’s Moon” to the Choctaw, and the “Moon When All Things Ripen” to the Dakota Sioux. It rises against the stars of Capricornus about a half-hour after sunset. August 13 Peak of the Perseid Meteor Shower, an annual favorite that averages about 50 meteors per hour, but this year’s display is spoiled by the light of a bright, waning gibbous Moon. Some brighter meteors might still be visible, radiating from the constellation Perseus, which is located in the northeast at about midnight. August 24 Uranus at opposition. The seventh planet rises at sunset against the faint stars of Aquarius, looking like a green star. It is usually only marginally visible without optical aid, but experienced observers can find it fairly easily with binoculars or a small telescope. August 27 New Moon. August 28 Mars at opposition! See boxed article for details. September 10 Full Moon rises about a half-hour after sunset between the stars of Aquarius and Pisces. September 23 Fall equinox (beginning of autumn) for the Northern Hemisphere at 3:48 a.m. pdt. September 25 New Moon at 8:08 p.m. pdt. The sunset of the first new crescent closest to the Fall equinox marks Rosh Hashanah, the Jewish New Year. September 29 Winter begins in the Northern Hemisphere…of Mars.
Times are for San Francisco, CA, and will vary for other locations. Planets Mercury Although at greatest elongation (separation from the Sun) on August 14, the speediest planet is still unfavorably positioned for viewing because it’s so low in the sky. An evening object in July and August, Mercury is visible low in the west after sunset and passes less than a half-degree from Jupiter on July 25. On July 30, it’s within a fifth of a degree of the star Regulus, with a thin crescent Moon nearby. Disappearing into the glow of the Sun by mid-August, it reappears in the morning sky in mid-September. Rising before dawn and making an almost vertical leap from the eastern horizon toward Jupiter, Mercury approaches within 7 degrees of the larger planet on September 26. Venus The brightest of the planets has one close encounter with Saturn on the mornings of July 7 and 8, drawing to within a degree of the ringed planet. It’s a challenge to see, occurring very low in the east-northeast just before dawn. For the rest of the season, Venus is too close to the Sun to be observed. Mars Doubling its brightness in July, the Red Planet slowly draws toward its closest approach to Earth in recorded history, which occurs in August. At the beginning of the month, it rises in the east around midnight against the faint stars of Aquarius. In August, its bright disk should be large enough to discern even through binoculars. The Moon passes very close to Mars on the evenings of July 16, August 12, and September 8. Jupiter Visible at the beginning of July low in the west at sunset, the largest of the planets is gradually washed from view by the end of the month. In conjunction with the sun on August 22, it doesn’t reappear in the morning sky until about mid-September, located low in the east against the stars of Leo. The Moon can be seen nearby on the mornings of September 23 and 24. Saturn Having passed conjunction in June, the Ringed Planet only gradually becomes visible in the morning sky by the end of July, rising in the east-northeast before dawn. It rises slightly earlier each day, and in August precedes the Sun by at least three hours. By September, it rises just after midnight against the stars of Gemini. Look for the Moon nearby on the mornings of July 26, August 23, and September 19 and 20.
Bing F. Quock is Assistant Chairman of the Morrison Planetarium. |