Last updateWed, 27 Sep 2017 1pm

29 Dec 2017

January Astronomy: The Second Full Moon of the Month Brings With It an Excellent Total Lunar Eclipse

Written by 

In January 2018, mornings are when most of the action takes place. The predawn sky hosts as many as four planets, including close pairings—Mars-Jupiter on Jan. 4-9, and Mercury-Saturn on Jan. 11-14.

Also: January has two full moons! Follow the waning moon mornings in first half of month, and watch it pass the four planets—Mars-Jupiter on Jan. 11, and Mercury-Saturn on Jan. 14 and 15.

Finally, don’t miss the total lunar eclipse on Jan. 31!

Evenings offer no naked-eye planets, but they do offer a waxing moon Jan. 17-30, and an uncommonly large number of bright stars with the appearance of Sirius, the brilliant “Dog Star” in the east-southeast.

Our New Year starts out with a “Supermoon,” the closest of 2018. As seen from Palm Springs, the full moon on Jan. 1 rises as the sun sets, at 4:49 p.m. A few minutes later, look for the huge disk of the moon resting on the horizon in the east-northeast. The moon will be up all night, setting at 7:17 a.m. on Jan. 2, some 26 minutes after sunrise.

Despite the full moon of Jan. 1 being the closest of the year, it is not the brightest. Brightest-moon honors for 2018 go to the next full moon, on the morning of Wednesday, Jan. 31. That moon’s greatest brilliance will occur just before the eclipse, when the moon is just outside of Earth’s shadow and reflecting the greatest amount of light our way. During the total eclipse itself, we’ll also experience the faintest full moon of the year, cut off from direct sunlight by the Earth’s shadow.

Here is your guide to the “blue” moon (the second full moon of a calendar month, by one definition) and total lunar eclipse, on the night of Tuesday, Jan. 30, and Wednesday, Jan. 31. Keep in mind that because of the mountains surrounding the Coachella Valley, rising times may be later and setting times may be earlier than the “ideal” times listed here. From many locations in the valley, the later stages of the lunar eclipse might be hidden behind mountains to the west.

If you can allot just a small amount of time to watch the eclipse, be in a dark place on Wednesday morning, Jan. 31, between 4:20 a.m. (the moon halfway into umbra) and 5:30 a.m. (mid-totality, when the moon in deepest eclipse). Dress warmly!

On Tuesday, Jan. 30, from Palm Springs, moonrise occurs at 4:37 p.m., with sunset at 5:16 p.m. Does the rising moon seem unusually large to you? It was closest to Earth earlier on Jan. 30, around 2 a.m. By 5:45 p.m., the moon is 12 degrees up in east-northeast to east, and Sirius, the brightest star, will be nearly 45 degrees farther to the right, in the east-southeast to southeast.

As twilight deepens, the entire Winter Hexagon becomes visible. Astronomical twilight ends at 6:41 p.m., and the sky in this brightly moonlit night will get no darker until the eclipse gets underway. As twilight ends, note Pollux 15 degrees above and a little left of the moon, and his twin, Castor, 4.5 degrees to the upper left of Pollux. By 7:30 p.m., the star Regulus, heart of Leo, is 10 degrees up, just north of east, and 24 degrees to the lower left of the moon.

In the hour between 10 and 11 p.m., use binoculars or a telescope to try to catch the Beehive star cluster—then a difficult target in a bright sky, only 2 degrees north of the full moon. We’ll have a very good look at the Beehive during tonight’s total lunar eclipse! By 11:15 p.m., the bright, golden orange star Arcturus is 10 degrees up in the east-northeast.

At 11:45 p.m., the moon reaches its high point in the sky, 16 degrees south of overhead. Notice how short your shadow is. By midnight, the star Spica in Virgo is 12 degrees up in the east-southeast. You can use the curved handle of the Big Dipper to locate Arcturus and Spica.

If you can still see Aldebaran above the mountains to your west at 12:38 a.m. (22 degrees up in the west), then from the same location, you will be able to view the moon at the start of total eclipse at 4:52 a.m.—because the totally eclipsed moon will very closely follow Aldebaran’s track across the sky, but nearly 4 1/2 hours later. If Aldebaran still appears above the mountains at 1:15 a.m., then you will be able to view the moon during its deepest total eclipse later that morning, at 5:30 a.m. If Aldebaran is still visible at 1:52 a.m., then from the same site you may be able to observe the moon at the end of total eclipse, at 6:08 a.m., provided the shadowed moon is bright enough to be seen in the brightening twilight.

At 1:52 a.m., can you spot Vega, only 4 degrees up in the northeast? For the rest of the night, it climbs higher, while Rigel, Aldebaran, Sirius and Betelgeuse will all set before 3:30 a.m., before the moon begins to enter the umbra, or dark central core of Earth’s shadow at 3:48 a.m.

By 2 a.m., bright Jupiter will be 10 degrees up in the east-southeast and 27 degrees to the lower left of Spica.

At 2:51 a.m., the moon will just begin to enter the penumbra, or outermost, lightest part of Earth’s shadow. At that time, with the moon’s disk just outside the shadow, the moon appears at peak brilliance, because it’s closest to being directly opposite to the sun without being in shadow. The outer portion of the penumbra is not detectable, and so duskiness at the moon’s eastern (upper left) edge won’t be noted for perhaps another half hour.

By 3:30 a.m., the penumbral darkening on the moon’s upper left edge will be noticeable. At that time, find Jupiter 25 degrees up in the southeast, and Mars 12 degrees to Jupiter’s lower left. Look for the red supergiant star Antares, heart of the Scorpion, within 9 degrees below Mars.

At 3:48 a.m., the moon begins to enter the umbra, or dark central core of the Earth’s shadow. The moon will then be nearly due west, 35 degrees up. Within a few minutes, a dark, noticeably curved circular edge of Earth’s shadow will project on the eastern (upper left) portion of the moon. At first, the shadow appears very dark, in contrast with the rest of the moon’s disk, still illuminated by partial sunlight.

By 4:19 a.m., Earth’s shadow reaches halfway across the moon’s disk. As more of the moon is immersed within the umbra, colors within the shadow become noticeable, from sunlight which has passed through Earth’s atmosphere and bent into Earth shadow toward the moon. The inner portion of Earth’s shadow is typically reddish in color, for the same reason that sunrises and sunsets appear reddened, and skies appear blue.

Soon after 4:30 a.m., watch for Saturn, just risen in the east-southeast, 32 degrees to the lower left of Mars, and 44 degrees to the lower left of Jupiter; and Altair, just risen about 10 degrees north of east.

Total eclipse begins at 4:52 a.m., when the moon becomes completely immersed within the umbra. At that time, the moon will be just north of due west, and 22 degrees up. The view will be stunning some 10 minutes earlier, while a narrowing bright crescent of sunlight still illuminates the west-southwest (lower) edge of the moon.

Near the start of total eclipse at 4:52 a.m., expect a large range of color and brightness on the moon’s disk. The outer edge of Earth’s shadow might be bluish or yellowish, with the inner portion a darker rusty or grey. Check against Danjon’s 5-point scale (L = 0 to L = 4) if you would like to rate and report the darkness and color of this lunar eclipse. Now is also the best time to use your binoculars to easily observe the Beehive star cluster, just 4 degrees to the lower right of the moon.

Astronomical twilight begins at 5:18 a.m., when the sun is 18 degrees below the eastern horizon. If you’re in a dark place, this is the best time for viewing the Milky Way. Look for the Cygnus Star Cloud about 20 degrees up in the east-northeast, within the Summer Triangle. Binoculars resolve the cloud into many stars! Look also for Saturn 9 degrees up in the east-southeast to southeast, 32 degrees to the lower left of Mars, and 25 degrees to the lower left of Antares. Arcturus will be just 15 degrees south of overhead.

Deepest eclipse occurs at 5:30 a.m., when the moon will be 10 degrees north of due west and just 14 degrees above the horizon.

As morning twilight continues to brighten, the totally eclipsed moon might fade into invisibility, depending on how dark the Earth’s shadow is during this eclipse. During some past total lunar eclipses, such as one I saw in December 1963, such little sunlight made it through our atmosphere into Earth’s shadow that the moon almost completely disappeared, even when high in a dark sky. That eclipse was preceded by a major volcanic eruption in Indonesia.

Total eclipse ends at 6:08 a.m., when the moon will be 15 degrees north of west, and just 7 degrees up. Jupiter will then be almost due south, 39 degrees up. Even if the totally eclipsed moon had previously faded into twilight, the moon partially emerged from Earth’s shadow may become visible again before it finally sets. In theory, someone on a high peak near Palm Springs would be able to view the sun and a partially eclipsed moon, simultaneously on opposite horizons, at 6:46 a.m.

If you miss the total lunar eclipse on Jan. 31, another will be visible from the Coachella Valley in just less than a year—during convenient evening hours. On Jan. 20, 2019, a 3.3-hour encounter of moon with Earth’s umbral shadow will begin at 7:34 p.m. PST, including a 62-minute totality starting at 8:41 p.m.

On Friday, Jan. 5, I will present a summary of the coming year’s sky events. The talk will be held at the Portola Community Center, 45480 Portola Ave., in Palm Desert. Doors open at 6:30 p.m. for refreshments, and the talk begins at 7 p.m.

The website of the Astronomical Society of the Desert at has a listing of our evening star parties at two locations. The primary, more accessible location is at the visitor center of the Santa Rosa and San Jacinto Mountains National Monument (on Highway 74, within four miles south of Highway 111 in Palm Desert). A session is scheduled there on Saturday, Jan. 20, from 5 to 8 p.m. Sawmill Trailhead, our high-altitude site (4,000 feet—wear warm clothes), will have a star party starting at dusk on Saturday, Jan. 13. The website includes maps and directions for both locations. Star parties can be cancelled in poor observing weather. See also the link to “Impromptu Star Parties.”

Also, check out the Sky’s the Limit Observatory and Nature Center in Twentynine Palms, at

To help you plan evening or morning planet viewing sessions during the year 2018, below is Jeffrey Hunt’s two-page graphic summary of moon and planet setting and rising times, relative to times of sunset and sunrise, exact for Palm Springs.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. 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. Dr. Jeffrey L. Hunt, a retired planetarium director now living in the Chicago area, has taught astronomy and sky watching to all ages. He studied astronomy education at Abrams Planetarium at Michigan State University. Jeff writes an astronomy blog at and can be followed on Twitter at @jeff_hunt.

Leave a comment

Make sure you enter all the required information, indicated by an asterisk (*). HTML code is not allowed.