Friday, October 4
New Moon occurs at 8:35 p.m. EDT. At its new phase, the Moon crosses the sky with the Sun and so remains hidden in our star’s glare.

Saturday, October 5
The Moon’s absence from the morning sky these next two weeks provides observers with an excellent opportunity to view the zodiacal light. From the Northern Hemisphere, the time around the autumnal equinox (which occurred two weeks ago) is the best for viewing the elusive glow before sunrise. It appears slightly fainter than the Milky Way, so you’ll need a clear moonless sky and an observing site located far from the city. Look for a cone-shaped glow that points nearly straight up from the eastern horizon shortly before morning twilight begins (around 5:30 a.m. local daylight time at mid-northern latitudes). The Moon remains out of the morning sky until October 17, when the waxing gibbous returns and overwhelms the much fainter zodiacal light.

Sunday, October 6
If you have a flat, unobstructed horizon toward the west-southwest, you can view a fine conjunction of solar system objects this evening. A 2-day-old Moon lies in the same binocular field as Mercury and Saturn. If you view from North America 30 minutes after sunset, you will find Mercury 2° south (lower left) and Saturn 3° northeast (directly above) the crescent Moon.

Monday, October 7
The Moon climbs higher in this evening’s sky, where it appears directly to the right of brilliant Venus. The two lie some 10° above the southwestern horizon 45 minutes after sunset. The planet shines at magnitude –4.3, far brighter than any other point of light in the sky. The Sun illuminates 10 percent of the waxing crescent Moon, but look carefully at the rest of its face and you should see the faint glow of earthshine. By tomorrow evening, the 18-percent-lit Moon stands above Venus.

Tuesday, October 8
The variable star Algol in Perseus reaches minimum brightness at 12:04 a.m. EDT tomorrow morning, when it shines at magnitude 3.4. If you start tracking it this evening, you can watch it more than triple in brightness (to magnitude 2.1) in the span of a few hours. This eclipsing binary star runs through a cycle from minimum to maximum and back every 2.87 days. Algol remains visible all night, passing nearly overhead around 3 a.m. local daylight time.

Wednesday, October 9
Mercury reaches greatest elongation today, when it stands 25° east of the Sun. Unfortunately for observers at mid-northern latitudes, the innermost planet barely scrapes the western horizon just after sunset. From 40° north latitude, it stands only 3° high 30 minutes after the Sun goes down. You’ll need a flat, unobstructed horizon and a pristine sky to see the planet. Fortunately, it shines brightly at magnitude –0.1. Use binoculars and you should also spy the 1st-magnitude planet Saturn, which lies 5° north (to the upper right) of Mercury these next few evenings.

Thursday, October 10
The Southern Taurid meteor shower reaches its peak this morning. Although this minor shower produces only five meteors per hour at best, its maximum falls well after the Moon sets. The radiant — the point from which the meteors appear to emanate —climbs highest in the sky around 2 a.m. local daylight time. (Despite the shower’s name, the radiant actually lies in northern Cetus at the peak.) Southern Taurid meteors tend to be bright and move more slowly than typical meteors. You also may see a few Orionid meteors during the predawn hours. Although this annual shower won’t peak until October 21, the Moon-free morning sky this week offers better viewing prospects than the waning gibbous Moon will on the 21st. You can tell a Southern Taurid from an Orionid meteor because Orionids appear to radiate from the constellation Orion.

The Moon reaches perigee, the closest point in its orbit around Earth, at 7:14 p.m. EDT. It then lies 229,792 miles (369,814 kilometers) away from us.

Friday, October 11
Shining at magnitude –2.2, Jupiter stands out among the background stars of Gemini the Twins from the time it rises shortly before midnight local daylight time until twilight is well underway. This week, Jupiter lies about two-thirds of the way to the zenith in the southeastern sky as morning twilight commences. A telescope shows Jupiter’s 39"-diameter disk and at least two parallel dark belts in its atmosphere. But the biggest treat for observers tonight is a rare triple shadow transit — the shadows of three of the planet’s four big moons simultaneously appear against the jovian cloud tops. Callisto’s shadow starts to cross the planet’s disk at 11:12 p.m. EDT, followed by Europa’s shadow at 11:24 p.m. and then Io’s shadow at 12:32 a.m. Saturday morning. All three black dots pock Jupiter’s atmosphere until Callisto’s shadow lifts back into space at 1:37 a.m. Io’s leaves next, at 1:48 a.m., while Europa’s is the last shadow standing until 2:01 a.m. The next such triple shadow transit will take place June 3, 2014, and the one after that on January 24, 2015 — but you’ll have to wait until 2032 to see another.

The First Quarter Moon appears almost due south as darkness falls this evening. The half-lit orb then sinks slowly toward the western horizon, where it sets shortly after 1 a.m. local daylight time. Our satellite officially reaches First Quarter phase at 7:02 p.m. EDT, when it lies in the northwestern corner of Capricornus. Observers across most of the United States and Canada can see the Moon occult (pass directly in front of) the 3rd-magnitude star Beta (β) Capricorni during the evening hours.

Saturday, October 12
The night sky’s most conspicuous harbinger of winter now rises in the east around midnight local daylight time. The constellation Orion the Hunter appears on its side as it rises, with ruddy Betelgeuse to the left of the three-star belt and blue-white Rigel to the belt’s right. As Orion climbs higher before dawn, the figure rotates so that Betelgeuse lies at the upper left and Rigel at the lower right of the constellation pattern.

Sunday, October 13
Mars rises around 3 a.m. local daylight time and climbs some 30° above the eastern horizon by the time twilight begins. Mars resides among the background stars of Leo the Lion, less than 2° above that constellation’s brightest star, Regulus. At magnitude 1.6, Mars appears slightly fainter than the star. Although you wouldn’t know it by looking at Mars with naked eyes or through binoculars, another solar system object lies in its vicinity. Incoming Comet ISON (C/2012 S1) currently lies 1° north of the planet and glows around 11th magnitude, which puts it within range of 6-inch telescopes under a dark sky. For more information about observing ISON, see “Comet ISON brightens before dawn” in the October issue of Astronomy.