Geminid meteor shower

Geminid meteor shower, 2012 © Mike Lewinski

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Know what's up.

The Morrison Planetarium's Skywatcher's Guide is a quarterly compendium of astronomical happenings.

July 6

Moon at last quarter, rising in the east at shortly after 1 am and located against the stars of Pisces the Fishes. By dawn, look for it in the southeast. It remains visible in full sunlight until it sets at midday.

Earth is farthest from the Sun (aphelion). Occurring during Summer in the Northern Hemisphere, this shows that Earth's distance from its star has less of an effect on the seasons than the 23½-degree tilt of the planet's axis of rotation, which causes variations in the angle and duration of sunlight shining on given areas on the planet's surface.

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July 12

New Moon at 7:48 pm. Occurring very close to lunar perigee (the Moon's closest approach to Earth), this will cause higher tides than usual due to the combined gravitational pulls of the Sun and the Moon.

Sighting of the first crescent after this New Moon marks the start of the eleventh month of the Moon-based Islamic calendar, known as Dhul-Qi'dah. This sighting is possible only from the Pacific Ocean on the 13th, but not from any major land area. It is more widely visible across the world after sunset on the 14th.

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July 19

Moon at first quarter, rising around 1:30 pm, lit from the west, illuminating the dark patches called the Sea of Serenity, the Sea of Tranquility, the Sea of Fertility, the Sea of Nectar, and the Sea of Crises. These are not really bodies of water, as early skywatchers thought, but flat plains of dried lava, although the Latin term for "sea"—"mare" (plural "maria")—is still used today.

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July 27

Full Moon, also called the "Buck Moon" or "Thunder Moon" (Algonquin), the "Killer Whale Moon" (Haida), and the "Moon of the Giant Cactus" (Pima).

This full Moon passes through Earth's shadow, causing a total lunar eclipse, occurring when the Moon is centered over the Indian Ocean and therefore not visible to observers in the US. However, skywatchers in eastern Africa, the Middle East, India, and parts of the Antarctic will see the eclipse in its entirety as the Moon becomes immersed in the reddish-brown shadow of our planet.

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July 28

Peak of the Delta Aquarid meteor shower, which is usually active from July 12 to August 23, and peaking on July 27 and 28, producing up to 20 faint meteors per hour radiating from Aquarius the Water-Carrier. This year, however, since the peak coincides with a full Moon, many of the meteors will be washed from view.

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August 4

Last quarter Moon rises shortly after midnight during the early hours before dawn against the stars of Cetus the Sea Monster and is high in the south by sunrise, lit from the left-hand side.

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August 11

New Moon. Like last month, this almost coincides with lunar perigee, causing higher tides than usual.

Sighting of the first crescent after new marks the start of Dhul-Hijjah, the 12th month of the Islamic calendar. This sighting is possible across most of the world just after sunset on August 12.

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August 12

Peak of the annual Perseid meteor shower, with very favorable prospects for this year's display. See Notes.

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August 18

First quarter Moon at 12:49 am. With binoculars—or better yet, a telescope—scan up and down the terminator (the line dividing the Moon's daytime and nighttime sides) for the long shadows of craters and mountains.

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August 26

Full Moon, known to the Choctaw as the "Women's Moon," to the Dakotah Sioux as the "Moon When All Things Ripen," and to the Mohawk as the "Time of Freshness."

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September 2

Moon at last quarter, rising just after midnight on the 3rd against the stars of Taurus the Bull and quite close to the star Aldebaran, which represents the Bull's eye. At dawn, look for it very high in the southeast—nearly as high as the Moon can get.

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September 9

New Moon, which is the start of the lunar cycle, or "lunation." Sighting of the first crescent after new marks the start of Muharram, and is possible from most of the Americas and most of Africa just after sunset on the 10th, and more easily from the rest of world on the 11th.

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September 16

Using last week's new Moon as a starting point, the Moon completes the first quarter of its orbit around Earth today. It generally rises at midday, is high in the south at about sunset, and sets around midnight. We see exactly half of its Earth-facing side, illuminated from the right.

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September 22

Equinox at 6:54 pm, PDT. For the Northern Hemisphere it's the Fall or Autumnal equinox. However, for the Southern Hemisphere, where the seasons are reversed because of Earth's axial tilt, it's the Vernal or Spring equinox. For clarity and to avoid confusion, many refer to it as the "September equinox," since the month is the same on either side of the equator, even if the seasons are opposite.

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September 24

Full moon. As the first following the equinox, this is traditionally called the "Harvest Moon." For about a week around this date, the difference in moonrise times from night to night is shortest, extending the period of usable light in the sky after sunset and allowing farmers to continue working in the fields, harvesting crops without interruption.

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