Events in the calendar are expressed in local time unless otherwise indicated. Sept. 1: The moon crosses the narrow corridor of Scorpius tonight just before reaching first quarter phase (at 5:30 a.m. Eastern standard time Sunday). Two reddish objects nearby are Antares (brightest star in Scorpius) below and Mars to the left. The very bright object farther left, in Sagittarius, is Jupiter.
Sept. 2: After the moon passes them during the day, Antares and Mars are both to its right, Mars the higher and a bit brighter. Mars also slips past Antares from right to left about 10 p.m. EST and then moves west from the star.
Sept. 3: Mercury skips past Regulus (Leo's bright star), still moving slowly west (retrograde) after inferior conjunction late last month. Both are too low at dawn to be interesting, but note their antics in the next few days.
Sept. 3-4: The moon highlights Jupiter, to its left on the night of the 3rd, it's right and more distant on the 4th, passing the planet (conjunction) about midnight Monday night. They set in Sagittarius after 11.
Sept. 6: Mercury stops moving west, hesitates, then takes up its direct (easterly) motion through the stars, the direction in which it moves in orbit.
Sept. 9-10: Full moon tonight at one minute past 2 a.m. on the 10th, still in Aquarius, south of Pisces. Fomalhaut, the bright star below it, is in Piscis Austrinus, the Southern Fish.
Sept. 11: Apogee moon (farthest from earth) is at the corner of Pisces with Cetus. Look below the moon tonight for Diphda, Cetus's brightest star.
Sept. 13: Mercury still hovers near Regulus, and today it reaches greatest westerly elongation, farthest right of the sun in its cycle of configurations.
Sept. 17-18: Moonrise is about 10 p.m. on the 17th. Last quarter moon is at 4 :31 a.m. EST Tuesday morning, just about dawn (when the moon is high in the south). The two stars visible above and below it are El Nath and Zeta Tauri, the ''horns'' of the Bull.
Sept. 21-22: Last chance to see the waning crescent moon this month. It's in Leo both mornings, above Regulus Saturday.
Sept. 23: Autumn begins in the Northern Hemisphere when the sun arrives at the autumnal equinox, exactly over Earth's equator.
Sept. 24: New moon (at 10:11 p.m. EST) and perigee (nearest earth) occur within minutes, causing the effect of perigee on the spring tide to concentrate on the tidal height rather than priming the time of the tide.
Sept. 26: Equal day and equal night occur today, not on the 23rd, but sunrise and sunset are not at 6 o'clock because of variations in local time. If the western sky is exceptionally clear tonight, look for the very slender two-day-old crescent moon.
Sept. 27: The moon is higher and a little thicker tonight, though not much more so. Still, it's easier to see, and you'll find Saturn just off its upper ''horn.''
Sept. 28-30: The thickening crescent moon comes into view higher in the west each evening, moving from Libra, through Scorpius and Ophiucus, and into Sagittarius, drawing closer to Mars and Jupiter.
On the night of the 30th, when it's just a day before first quarter, the moon passes Mars at about 8 p.m. EST, close enough to cover the planet in the southern and eastern Pacific.