| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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SKYGUIDE July to September 2001 July 5 Full Moon, known to the Choctaw as the “Crane Moon,” to the Tlingit as the “Moon When Everything is Born,” and to the Pima as the “Moon of the Giant Cactus.” As it’s just after Solstice, the Summer Sun follows a high daytime arc, and this Full Moon crosses the sky very low. A partial lunar eclipse can be seen from the Eastern Hemisphere. July 17 If you know exactly where to look, you can see Venus in the daytime. If the sky is clear at 10:10 a.m. PDT, West Coast observers with telescopes might see the waning crescent Moon move in front of Venus and block it from view (a lunar occultation of Venus.) The planet emerges again at 11:44 a.m. pdt. July 20 New Moon is not visible in the sky tonight, the 32nd anniversary of the Apollo 11 moon landing. Tomorrow night, look for a thin, day-old crescent low in the west after sunset. Can you see its dark face dimly illuminated by “earthshine,” the sunlight reflected off the face of the Earth? August 11 The Perseid meteor shower begins to peak, but this isn’t the best year to see it. This year, the last quarter Moon rises about midnight, generally the best time to start viewing the meteors. As a result, moonlight will hide the 50 or more meteors falling per hour. If it’s any consolation, the Moon is at a perfect phase to view through binoculars: scan along the day-night line for the stark shadows of mountains and craters. August 15 Daytime occultation of Jupiter by the waning crescent Moon at 1:21 p.m. pdt, with reemergence at 2:28 p.m. PDT. August 18 New Moon at 7:55 p.m. PDT. The Moon and the Sun are located in the same direction. Combined with perigee (the Moon’s closest distance to Earth), this results in a strong gravitational pull on Earth that causes higher tides than usual. September 2 Full Moon, known to the Micmac as the “Moose-Calling Moon,” to the Ponca as the “Moon When the Elk Bellow,” and to the Paiute as the “Moon Without a Name.” September 17 New Moon at 3:27 a.m. PDT. The first day of the Jewish year 5762 begins at sunset with Rosh Hashanah. September 22 Autumnal Equinox at 4:02 p.m. PDT. The Sun rises due east, sets due west, and spends equal time above and below the horizon. Mercury Rising before dawn in early July, the nearest planet to the Sun appears with brighter Jupiter on the mornings of the 11th to the 13th. It then retreats back into the Sun’s glow, disappearing from view by month’s end. It reappears in evening skies by late August, but never gets far enough above the horizon for stargazers to see it well. The best view of Mercury occurs low in the west and close to the bright star Spica after sunset on September 19. The crescent Moon passes close on the morning of July 19, August 19, and more distantly on the evening of September 18. Venus The brightest planet dominates the morning sky all season, rising before dawn and outshining everything save the Sun and Moon. It makes a number of beautiful predawn appearances. On July 15, it passes less than a degree from Saturn, when the disks of both planets appear the same size through a telescope. July 17, it forms a glorious triplet with Saturn and the waning crescent Moon. Later that day, North American observers using a telescope can see the Moon passing before Venus at 10:10 a.m. pdt. On August 5, Venus passes about a degree from Jupiter. The Moon sweeps by again on August 16 and September 15, and Venus passes near the star Regulus, heart of Leo the Lion, September 20 & 21. Mars Just past opposition, Mars remains bright, rising in the east at sunset. In July, it’s at the foot of Ophiuchus the Serpent- Bearer and crosses into Sagittarius on August 31st. It’s in retrograde motion (moving east to west against the stars) until July 19, resuming its usual direction when about six degrees from the red star Antares in Scorpius. The Moon passes near Mars the evenings of July 2, 29, and 30, August 26 and 27, and September 24. Jupiter The King of the Planets shines in the east against the stars of Gemini just before sunrise. Jupiter climbs higher each morning until it’s nearly overhead at dawn by the end of September. Look for it near Mercury on July 13, the waning crescent Moon on July 18, Venus on August 5, and the Moon again on August 15 (daytime occultation 1:21 p.m. pdt) and September 12. Saturn The Ringed Planet
is a predawn object in the east against the stars of Taurus, near the
red star Aldebaran, eye of the Bull. By September, it rises at about
midnight and is nearly
(Times indicated are for San Francisco, CA, and are accurate to within two minutes.)
Bing F. Quock is a member of the Morrison Planetarium staff at the California Academy of Sciences. bquock@calacademy.org |
Summer 2001
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