This month’s highlights include a total lunar eclipse in the predawn hours of Wednesday, Oct. 8, and a partial solar eclipse on Thursday afternoon, Oct. 23. Read more about these eclipses here.
The two eclipses make October a good month to follow the moon through an entire cycle of phases and observe its changing visibility in day and night skies.
1. Observe the moon in early evening, about one hour after sunset.
During the two-week periods Sept. 26-Oct. 8 and Oct. 25-Nov. 7, the moon changes from a thin crescent low in the southwestern sky, and moves through first quarter phase. By the final date of each set, Oct. 8 and Nov. 7, the moon will have just passed through full phase and will rise north of east, in waning gibbous phase—a little less than full—within an hour after sunset.
Our evening twilight all-sky chart above depicts the sky at dusk (mid-twilight), when the sun is 9 degrees below the horizon, about 40 minutes after sunset at this time of year. Those plotted on our evening chart are the first to appear as twilight fades after sunset. October’s brightest stars at dusk are Arcturus in the west, and Vega nearly overhead. Also high in the sky are Altair and Deneb, completing the Summer Triangle with Vega. Mars lingers in the southwest all month, while Antares, just 4 degrees from Mars on Oct. 1, sinks into the southwest as the month progresses. Saturn, on its way to conjunction beyond the sun in mid-November, sinks into the west-southwest. Fomalhaut, mouth of the Southern Fish, climbs into the southeast.
On Oct. 25, use binoculars to catch Saturn within 5 degrees to the lower right of the thin crescent moon, and Antares 8 degrees to the lower left of the moon on the next evening. On Oct. 27 and 28, find Mars 9 degrees to the left of the moon on the first evening, and about the same distance to its lower right on the next.
2. Watch the moonrise each day when it occurs between sunset and 10 p.m.
In October 2014, this happens Oct. 8-12. On Oct. 8, the moon rises just after sunset. (The full moon and the total lunar eclipse will have occurred earlier on the same date, before sunrise.) Thereafter, the moon rises later each evening. Pick a spot with a good view of the eastern horizon, and enjoy the show. Note the color of the rising moon, and—if you can observe from the same location each evening—note the time and the place along your horizon panorama where the moon rises.
3. Look for the moon each morning, about one hour before sunrise.
With daylight saving time still in effect in October, this shouldn’t be too much to ask. The dates this month 2014 are Oct. 8 (soon after the lunar eclipse has ended in California) through Oct. 22.
During these 15 mornings, the waning moon changes from full, low in the west on Oct. 8, and moves through last quarter phase, half full and 90 degrees west of the sun, on Oct. 15, to a thin crescent old moon, just risen within 10 degrees south of east, on Oct. 22.
While you’re out, use our morning twilight all-sky chart below to find these bright objects in morning twilight: Jupiter (magnitude -2); Sirius (-1.5); and Canopus(-0.7), very low in the south for Southern Californians. Mercury ranks next after it brightens past magnitude 0 on Oct. 28; Arcturus (mag 0.0), after it emerges late in month; and Capella (0.1).
As for morning planets: Jupiter climbs very high through the southeastern sky. One week after passing inferior conjunction on Oct. 16, nearly between Earth and the sun, backlit Mercuryemerges south of east as a faint +1.5 magnitude object on Oct. 23, and brightens rapidly to magnitude -0.6 by month’s end.
As for morning stars: The huge Winter Hexagon reaches its highest position in morning twilight this month. In clockwise order, its stars are Sirius, Procyon, Pollux (and Castor, not quite bright enough to be plotted), Capella, Aldebaran and Rigel. Betelgeuse is inside the figure, and bright Jupiter and faint Regulus pursue the hexagon across the sky. Arcturus, Mercury and Spica, in that order, appear above the eastern horizon in late October.
An hour before sunup, skies are dark enough to allow viewers to follow the moon’s changing place against background stars. On Oct. 11, the moon is 8 degrees south (to the lower left) of the Pleiades cluster, and on the 12th, just 1 to 2 degrees above Aldebaran, eye of Taurus.
On Oct. 13, the waning gibbous moon has moved 14 degrees east of Aldebaran and stands 12 degrees to the upper right of Betelgeuse, Orion’s shoulder.
On Oct. 15, the nearly last quarter moon—just more than half full and just more than 90 degrees from the sun—stands nearly equidistant from Procyon, the “Little Dog” star, and Pollux, the brighter of the “Twin” stars of Gemini. On the 17th, the crescent moon stands 7 to 8 degrees to the upper right of Jupiter.
On Oct. 18, the moon, a crescent one-quarter full, stands 8 to 9 degrees to the lower right of Jupiter and 6 to 7 degrees to the lower right of Regulus, heart of Leo, the Lion. On the next morning, the moon is 8 to 9 degrees below Regulus.
Finally, on the morning on Oct. 22, the old moon, less than 2 percent full, is just 2 degrees up an hour before sunrise, and 8 degrees south of due east. A partial solar eclipse occurs on the afternoon of the next day, Thursday, Oct. 23.
4. Observe moon in the morning.
At 9 a.m., follow the moon daily from Oct. 11 (88 percent full, low in the west to west-northwest), through last quarter phase on Oct. 15, just over half full and more than halfway up to overhead in the west-southwest. Your last easy morning daytime view at that hour may occur on Oct. 20, when the moon will be a 10 percent crescent located 37 degrees to the upper right of the sun.
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, who provided the twilight charts, did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University. He remains active in research and public outreach in astronomy.