Northern Hemisphere gazer's guide

By , Director, The American Museum of Natural History

OCt. 1: Brilliant Venus and the slender four-day-old crescent moon should be visible tonight low in the west-southwest, beginning early in the evening twilight. The moon, well above Venus, sets about two hours after the sun, Venus somewhat earlier. This is a poor evening elongation for Venus. Even though it is brightening rapidly now (reaching maximum brilliancy in mid-December), and approaching greatest easterly elongation (in early November), the planet's position to the sun's east (left) at this time of year keeps it so far south that it sets early, relative to the time of sunset.

Oct. 2: The moon, located in tonight's sky just above Antares, the bright red star of Scorpius, is at apogee. At this point in its orbit, the moon is not only farthest from earth, it is also moving most slowly in the elliptical path it follows around earth (it moves most rapidly near perigee). It takes the moon over eight days from the last new moon (Sept. 27) to reach first quarter (Oct. 6 ), but less than seven days to go from full moon (Oct. 13) to last quarter (Oct. 19) this month. Perigee is on the 14th.

Oct. 4 - 5: The waxing crescent moon passes through Sagittarius. Look below it for the eight stars forming a "teapot," the best guide to Sagittarius.

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Oct. 5: Saturn is in conjunction with the sun, moving past it from left to right to enter the morning sky.

Oct. 6: Mercury is stationary among the stars, poised ofr its westerly (retrograde) motion before passing between sun and earth in about two weeks.

Oct. 11: The gibbous moon is below the Square of Pegasus tonight. Look for four stars above the moon arranged like a box, with its sides north-south and east west. At about 8 p. m. Eastern standard time, the moon is just below the vernal equinox, sometimes called the first point of Aries. But the moon will not be in Aries until the 13th!

Oct. 13: This is the night of the Hunter's Moon, full today, but appearing full or nearly full, and setting at or very shortly after sunset for the next three nights.

Oct. 14: It's Jupiter's turn to pass the sun, from left to right, in conjunction with it. After giving us some pretty interesting combinations with Saturn (remember the triple conjunction, you won't see another one in your lifetime!) and Venus, it leaves the evening sky, joining Saturn as a morning star.

Oct. 17: The reddish star below Venus tonight is Antares, in Scorpius. But look early in the waning twilight; they set early.

Oct. 18: Mercury is in inferior conjuction, passing between sun and earth, moving to the sun's right to enter the morning sky. Though it's been a poor evening star over the past two months, it will become a fairly good morning star late this month.

Oct. 19: The news is in the morning sky today. Look before the dawn. In the south, the last quarter moon is just below Castor, one of the two bright "twin" stars of Gemini. To their left, in the southeast, you will see another pair of twins, Mars and Regulus, the bright star of Leo.

Oct. 21: The Orionid meteor shower is at maximum this morning, best from 2 a.m. on. Not particularly productive (about 25 shower meteors per hour), but some very bright meteors result from this swift stream, believed to be associated with Halley's Comet.

Oct. 22: The waning crescent moon passes Regulus and Mars today. Look for all three close to one another before dawn this morning, with the moon between Regulus (to its right) and Mars.

Oct. 25: Communities using daylight time adjust to standard time early today by shifting their clocks one hour backward.

Oct. 26: Mercury ends its retrograde (westerly) motion through the stars, having passed between earth and sun about a week ago, and resumes its normal easterly motion.

Oct. 30: The moon is at apogee for the second time this month.

Oct. 31: The crescent moon again passes above Venus. Though Venus sets well before the moon, its brightness should allow you to see it low in the southwest after sunset.

All Month: We had a sky full of evening stars last month, though not always well placed for viewing. but it all falls apart in October, when Mercury, Jupiter, Saturn, and Pluto shift into the morning sky. The only planet easily seen in the evening sky this month is Venus, and that only because it is bright enough to stand out in the early twilight after sundown. Look into the west from about half an hour after sunset.

The morning sky, though filling up with planets, isn't much better. Mars is the only bright planet in good position, well up in the southeast by daybreak, but unfortunately rather dim. However, it can be recognized by its proximity to Regulus, in Leo, especially late in October. Mercury, Jupiter, and Saturn give promise to be good morning stars in early November.

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