On Thursday morning, Sept. 29, a beautiful sight will reward early risers who go out to enjoy the brightening dawn 45 minutes to an hour before sunrise: About 5:45 a.m. in the Coachella Valley that morning, very low, almost directly east, a slender, crescent old moon will be suspended just 2 degrees below Mercury.
Other sights in the morning sky through October include Sirius, the brightest star, well up in the south-southeast, and the rest of the Winter Hexagon’s stars—in clockwise order, Procyon, Pollux (and Castor, not shown), Capella, Aldebaran and Rigel, with Betelgeuse inside. Other bright stars include Canopus, very low in the south, the second brightest star (easier to see later in the month, when it reaches its high point, due south, earlier in a darker sky), and Regulus, heart of Leo, the Lion, in the east.
The old moon of Sept. 29 is followed by the new moon on Fri. Sept. 30 at 5:11 p.m., invisible as it passes close to the sun. The next chance to see the moon is on the evening of Saturday, Oct. 1, only about 20 to 30 minutes after sunset. With all the mountains around us, you must choose your vantage point carefully, because about 20 minutes after sunset in the Coachella Valley, or about 6:50 p.m., the very slender crescent will be only 3 to 4 degrees up. Binoculars will help. Look for the hairline crescent 9 degrees south of due west and 20 degrees to the lower right of Venus. This crescent moon is special, because its sighting marks the beginning of the first month of the new year of the Islamic calendar.
The moon will be much easier to spot as it thickens, appears higher, and sets more than half an hour later nightly. On Sunday, Oct. 2, the moon will be 10 degrees to the lower right of Venus. On Monday, Oct. 3, the moon will pass within 5 degrees to the upper right of Venus, and on Tuesday, the moon will appear 13 degrees to the upper left of Venus. On Oct. 5, the moon passes within 5 degrees to the upper right of Saturn, and on Friday the 7th, the moon will be 7 degrees to the upper right of Mars.
Besides these three planets, other prominent objects at dusk include golden Arcturus sinking in the west, and blue-white Vega northwest of overhead, with Deneb and Altair, completing the Summer Triangle.
The full moon of Saturday, Oct. 15, rises just north of due east a few minutes after sunset that evening. The waning moon rises later each night, shifting farther north along the horizon nightly through Oct. 20.
In the Coachella Valley at 9 p.m. on the evening of Tuesday, Oct 18, binoculars will show a bright star within one degree to the lower left of the moon, just risen in the east-northeast. By 10:19 p.m., the sunlit edge of the moon will cover first-magnitude Aldebaran, eye of Taurus, the Bull. Aldebaran remains hidden by the moon until 10:35 p.m., when the star reappears along the northern part of the moon’s dark edge. Even though this is the brightest star the moon can occult (cover), a telescope will be needed to observe the star disappear and reappear, since the moon is very bright—only three days past full.
Watch the planets move! In the evening sky in October, Venus goes east 1.2 degrees per day against background stars, while Mars goes east about 0.7 degrees daily. Follow their progress easily from one night to next for several evenings around dates when planet passes a star. Track Venus for a few evenings around following dates when it passes close to a background star: Oct. 5, when Venus passes 0.8 degrees to the lower left of third-magnitude Alpha in Libra, also known as Zubenelgenubi, the southern claw of an early, larger version of the Scorpion; Oct. 20, when Venus passes within 1 degrees above second-magnitude Delta Scorpii, the middle of the three stars in the head of the Scorpion; Oct. 26, when Venus passes 3.1 degrees north (to the upper right) of first-magnitude Antares; and Oct. 29, when Venus passes 3.0 degrees south (to the lower left) of Saturn.
Watch Mars on Oct. 6, as it passes 0.2 degrees below third-magnitude Lambda Sagittarii, marking the top of the Teapot. This star is also known as Kaus Borealis, northern star of the Archer’s bow. On Oct. 15, Mars passes within 1.3 degrees north (to the upper right) of second-magnitude Nunki, or Sigma in Sagittarius, brightest star in handle of the Teapot.
Saturn, the only other bright evening planet, moves only 2.7 degrees east during Oct. 1-31, averaging less than 0.1 degrees per day.
In the mornings: Just before the start of twilight Sept. 29-Oct. 12 and Oct. 29-Nov. 11, from a very dark place, try to see the zodiacal light—from sunlight reflected off comet and asteroid dust in the plane of the solar system. Look for a huge pyramid of faint light extending upward from the eastern horizon toward the star Regulus in Leo.
Low in the east during morning twilight in October, bright, emerging Jupiter replaces Mercury. Using binoculars about 40 minutes before sunrise, see both planets for a few days around Oct. 11. The best mornings are Oct. 10-12: The planets are 1.5 degrees apart on Oct. 10, with Jupiter to the lower right of Mercury. They appear closest, 0.8 degrees apart, on Oct. 11, with Jupiter to the south (right) of Mercury. They’re 1.9 degrees apart on Wednesday, Oct. 12, with Jupiter to the upper right.
On Friday, Oct. 21, in the predawn darkness hours, watch for the peak of the Orionid meteor shower, consisting of particles from Halley’s Comet.
On Friday, Oct. 28, a waning crescent moon, two days before new, will appear 2-3 degrees to the lower left of Jupiter in morning twilight. On Saturday morning, Oct. 29, the last old crescent will appear 14 degrees to the lower left of Jupiter. Binoculars will help you pick out emerging Spica, just five degrees to the lower right of the delicate crescent. The new moon occurs on Sunday, Oct. 30, at 10:38 a.m.
On Monday evening, Oct. 31, 40 minutes after sunset, the young crescent moon will be 3 degrees up in the west-southwest, 24 degrees to the lower right of Venus.
The Astronomical Society of the Desert will host the next of our popular series of monthly star parties on Saturday, Oct. 8, from 7 to 10 p.m. They are held at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within 4 miles south of Highway 111 in Palm Desert. Check www.astrorx.org for listings of our high altitude star parties at Sawmill Trailhead starting at dusk. The next one will be held on Saturday, Oct. 22. Visit the website for maps and directions to both star party sites, and for dates and locations of lecture meetings. Also, follow the link to our “Impromptu Star Parties, which could be announced on short notice at any time.
Also, don’t miss the 2016 Joshua Tree National Park Night Sky Festival on Oct. 28-30 and the 2016 Nightfall Star Party in Borrego Springs Oct. 27-30.
The Wildlands Conservancy’s Whitewater Preserve at 760-325-7222 and the Pioneertown Mountains Preserve at 760-369-7105 occasionally host star parties. The next one at Pioneertown Preserve is set for Oct. 8. Reservations required; call the appropriate preserve.
Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.