Abrams Planetarium


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To the reader

The Skywatcher's Diary for December 1997 has been prepared by Robert C. Victor. Sometimes you can see next month's in advance by looking in our archives. Credit to Abrams Planetarium, Department of Physics and Astronomy at Michigan State University, together with mention of our Sky Calendar, would be appreciated.

A sample issue of Sky Calendar from a previous month is available over the Internet. It can be viewed via a World-Wide Web browser such as Netscape or Internet Explorer, directly at URL:


If you would like a printed sample of the December issue, send a long, self-addressed stamped envelope to:

December Sky Calendar
Abrams Planetarium
Michigan State University
East Lansing, MI 48824

Each month, the Department of Physics and Astronomy at Michigan State University also makes Skywatcher's Diary available over the Internet. It can be accessed via a World-Wide Web browser such as Netscape or Internet Explorer, directly at URL:


The Skywatcher's Diary is also available via anonymous ftp at: www.pa.msu.edu in the directory /pub/swd


December 1997 is a fine month for evening planets. Here's a summary:

Venus is spectacular in SW at dusk, setting 3 hours after sunset early in month and reaching greatest brilliancy. Try for Venus before sunset, when binoculars and telescopes show its crescent, larger and thinner as weeks pass.

Mars is nearby all month, within 7 degrees to Venus' lower right on Dec. 1, just 1.1 degrees to its lower left on Dec. 21, and 8 degrees to its upper left on Dec. 31. Mars is less than 1/200 as bright as Venus.

Mercury may be glimpsed very low in SW Dec. 1-9, while fading daily, 23 to 26 degrees to Venus' lower right. Binoculars may be needed to spot Mercury in evening twilight glow, especially from N states. Mercury brightens low in SE sky as a morning "star" on Dec. 24-31, staying 11 degrees from Antares.

Jupiter shines in SSW to SW at dusk, to Venus' upper left. Venus and Jupiter are 23 degrees apart on Dec. 1, 17 degrees apart Dec. 15-26, and 19 degrees apart Dec. 31. Jupiter is only 1/10 as bright as Venus, but still outshines the brightest stars.

Saturn is in ESE to SSE at dusk, a lonely "star" 57 to 52 degrees E of Jupiter.

The Moon is near planets at dusk Dec. 1, 2, 3, 4, 8, and Dec. 30-Jan. 1, and near Mercury at dawn on Dec. 27 and 28. Young crescent Moon at dusk on Dec. 30 marks start of the Islamic holy month of Ramadan. Moon occults (covers) Saturn night of Dec. 8-9 for Hawaii and most of western U.S. Moon occults Aldebaran on night of Dec. 12-13 for most of U.S. For more on both occultations: See pp. 100-101 of December Sky & Telescope, Skywatcher's Diary below, and http://www.sky.net/~robinson/iotandx.htm

Monday, December 1

For the first four evenings of December and again on Dec. 8, the Moon appears close to a different planet each night. This evening is Mercury's turn, although observers in northern states will need binoculars to see it. About 45 minutes after sunset, look very low in SW, 6 degrees lower left of the nearly 2-day-old crescent Moon. Both are 23 degrees lower right of Venus, the brilliant "evening star." Bright Jupiter is the same distance to Venus' upper left, and faint Mars becomes visible within 7 degrees to Venus' upper left as sky darkens. At nightfall Saturn is a bright lonely "star" on SE, 57 degrees upper left of Jupiter.

Tuesday, December 2

Face SW at dusk to find brilliant Venus about 11 degrees left of 3-day- old crescent Moon. Mars is between them but lower, about 6-1/2 degrees lower right of Venus. Jupiter is within 23 degrees to Venus' upper left.

Wednesday, December 3

With Venus near its greatest possible brilliance and close to the Moon this afternoon, this is an excellent day to spot Venus in the daytime. You can catch Venus when it's due south by following these steps: First, calculate the time when the Sun is highest and due south -- your local midday, which is halfway between the times of your local sunsrise and sunset. Pick a place to stand so the Sun then appears about 2 degrees above an object such as a flagpole or the peak of a roof. Return to that spot 3 hours 9 minutes later, and Venus will appear due south, just above the same object and about 6 degrees lower right of the Moon. Using binoculars, can you resolve Venus as a crescent? Today Venus follows the Sun by 3 hours 9 minutes, but on a path that is about 1.6 degrees lower than the Sun's path across the sky. Half an hour before sunset, Venus is in SSW, 6 or 7 degrees below the Moon. Forty-five minutes after sunset, the view is very striking: A 4-day-old crescent Moon with earthshine on its dark side, and Venus below. Note Jupiter 22 degrees to Venus' upper left, and Mars and Mercury 6 and 23 degrees to Venus' lower right.

Thursday, December 4

At dusk, face SSW to see a 5-day-old crescent Moon with bright Jupiter about 5 degrees to its left. To their lower right, in order of increasing distance, are brilliant Venus, faint reddish Mars, and Mercury, which is about to set. Saturn is high in SE.

Friday, December 5

At nightfall, the three brightest objects in the night sky lie in a nearly straight line in SSW to SW: The Moon, with Jupiter within 10 degrees lower right, and Venus in turn 21 degrees lower right of Jupiter. Look above Venus and lower right of Jupiter for a pair of naked-eye stars 2.4 degrees apart. The upper right member of these two stars, Alpha in Capricornus, appears to sharp-eyed observers as a close double star. Binoculars show Alpha easily "split" into a double, with bright Beta Capricorni in the same field, to lower left. A line from Alpha to Beta, extended about 4 degrees beyond Beta to lower left locates a compact triangle of 5th and 6th magnitude stars, Rho, Pi, and Omicron Capricorni. The planet Uranus is of similar brightness, a little more than a degree to the left of the triangle.

Saturday, December 6

The Moon passes First Quarter phase overnight, at 1:09 a.m. EST Sunday morning. So at sunset this evening, the Moon is nearly 90 degrees (a quarter-circle) left of the setting Sun. The Moon appears nearly half illuminated. In daytime just before sunset, can you locate Venus 42 degrees from Sun, nearly midway between Sun and Moon? As sky darkens, look for Mars 6 degrees lower right of Venus.

Sunday, December 7

At nightfall Saturn shines 18 degrees to Moon's left, and all four satellites of Jupiter found by Galileo can be seen in binoculars: Io very close to Jupiter's lower right, and Europa, Ganymede, and Callisto to the planet's upper left. In its 17-day orbit, Callisto will appear farthest to Jupiter's upper left on Tuesday, and farthest to lower right on Dec. 17 and 18.

Monday, December 8

Within an hour of midday (the time midway between sunrise and sunset), select a spot from where the Sun appears immediately above an object, mark the spot, and return there exactly 3 hours later. You'll find Venus in the same place in the sky the Sun had been!

Moon occults (covers) Saturn tonight for observers in Hawaii and most of western U.S. except Alaska and the Northern Tier (WA to northern MN). From eastern U.S. as far west as MI, OH, eastern parts of KY and TN, GA, and most of FL, Moon is 4 or 5 degrees west (right) of Saturn at dusk and creeps toward the planet by nearly one Moon- diameter each hour, but doesn't quite reach it by moonset. From places farther west, where an occultation is visible, the disappearance of Saturn at Moon's leading dark edge will be observable in binoculars, but a telescope is required to see reappearance at Moon's bright edge. Here are times Saturn is covered for selected cities. HST: Honolulu 8:04-9:29 p.m.; Hilo 8:08-9:34 p.m. PST: San Francisco 11:18 p.m.-12:14 a.m.; Los Angeles 11:19 p.m.-12:21 a.m.; San Diego CA 11:20 p.m.-12:23 a.m.; Portland OR 11:34-11:50 p.m. MST: Phoenix AZ 12:24-1:24 a.m.; Salt Lake City 12:27-1:14 a.m.; Denver 12:30-1:18 am. Disappearance only, CST: Austin and Little Rock 1:32 a.m.; New Orleans 1:33 a.m. (only 3 degrees up); Chicago 1:35 a.m. (1 degree up); Minneapolis 1:39 a.m.; Duluth 1:45 a.m. (3 degrees up). For maps to predict times of disappearance and reappearance of Saturn from your location, see p. 100 of December Sky & Telescope. The same article also has maps for this Friday night's occultation of Aldebaran. For more on both occultations, visit website of the International Occultation Timing Assocation at http://www.sky.net/~robinson/iotandx.htm

Tuesday, December 9

Face SE at dusk to find Saturn 10 degrees to upper right of gibbous Moon.

Wednesday, December 10

An hour after sunset, the three brightest night-sky objects are: Moon in ESE, Venus in SW, and Jupiter in SSW, 19 degrees upper left of Venus. Faint Mars is 5 degrees to Venus' lower right. Note the lineup, in order, of Mars, Venus, Jupiter, Saturn in SE, Moon, and Aldebaran just over 30 degrees to Moon's lower left.

Thursday, December 11

Venus is now at greatest brilliancy, mag. -4.7. At midday, pick a place so Sun appears just above an object such as a flagpole or peak of a roof. Return to same place 2 hours 54 minutes later, and Venus will be above same object but 1 degree higher than Sun was. Binoculars show Venus as a crescent, about one-quarter full and 0.7 arc-minute across. Just before sunset, Venus is easy for naked eye, 40 degrees to upper left of the Sun.

Friday, December 12

Moon occults Aldebaran tonight for all of U.S. except Alaska, southernmost Texas, southeasternmost Louisiana, and most of Florida. In the lower peninsula of Michigan, the time of disappearance of the star ranges from 11:52 p.m. EST on the western side of the state to 12:01 a.m. on the east. Reappearance time there ranges from 1:10 a.m. to 1:19 a.m.

Times Aldebaran is behind Moon for selected cities -- HST: Honolulu, star covered until 6:14 pm. PST: Los Angeles and San Francisco, star covered 7:51-9:04 pm; Seattle 8:10-9:13 pm. MST: Tucson 9:02-10:11 pm; Salt Lake City 9:08-10:24 pm; Denver 9:17-10:35 pm. CST: Kansas City MO 10:37-11:54 pm; Austin TX 10:39-11:23 pm; Chicago 10:51 pm-12:09 am; New Orleans 11:11-11:29 pm. EST: E Lansing MI 11:58 pm-1:15 am; Toronto 12:07-1:24 am; Pittsburgh 12:08-1:22 am; Atlanta GA 12:10 -1:02 am; Washington DC 12:16- 1:26 am; New York City 12:20-1:32 am; Boston 12:23-1:36 am.

For maps to predict times of disappearance and reappearance of Aldebaran from elsewhere in the country, see p. 101 of December Sky & Telescope. For more on this event, visit the website of International Occultation Timing Assocation at http://www.sky.net/~robinson/iotandx.htm

Saturday, December 13

From southern Michigan tonight, the Full Moon rises in ENE about 10 minutes after sunset. As the sky darkens, note the star Aldebaran about 11 degrees to the Moon's upper right, and the Pleiades cluster 14 degrees above Aldebaran. Tonight's "Moon before Yule" spoils the peak of this year's Geminid meteor shower. The greatest number of meteors are likely tonight between 10:30 p.m. and 5:30 a.m. local time.

As sunrise approaches on Sunday morning, try to keep the setting Moon in view as long a possible. Can you see the Sun and Moon simultaneously?

Sunday, December 14

About an hour after sunset tonight, keep watch in ENE for this month's northernmost moonrise. In another hour, the brightest stars of Orion, reddish Betelgeuse and blue-white Rigel, are in the east, 12 and 31 degrees to the Moon's right, while the Hunter's belt appears as a vertical line of three stars between them.

Monday, December 15

Tonight through Dec. 26, Venus and Jupiter, the two bright planets in the SW at dusk, remain 17 degrees apart. Late this month and in early January, Venus turns back toward the Sun, and the gap between the two planets will appear to widen. Not until April 23, 1998 will Venus finally appear to catch Jupiter. That spectacular conjunction of bright planets will take place in the eastern morning sky.

At nightfall, look for Mars 3.5 degrees lower right of Venus. Binoculars show 6th-magnitude Uranus 4.7 degrees to Venus' upper left.

An hour before sunup on Tuesday, Moon is in west with Procyon 12 degrees lower left, and Pollux, one of the Gemini twins, nearly as far to Moon's upper right. Castor, the other twin, is 4.5 degrees right of Pollux.

Tuesday, December 16

An hour before sunup on Wednesday, in the western sky, locate Procyon, the brightest star in Canis Minor, the Little Dog, 16 degrees below the Moon, and the Gemini twins, Pollux and Castor, 17 to 21 degrees to Moon's right.

Wednesday, December 17

Four hours after sunset, locate Orion in ESE and follow his belt downward to Sirius, the Dog Star. Procyon, low in east, completes the nearly equilateral Winter Triangle with Sirius and Betelgeuse, Orion's shoulder.

An hour before sunup Thursday, Moon is in WSW with Regulus 11 degrees upper left.

Thursday, December 18

An hour before sunrise on Friday, Moon is in SW with Regulus, heart of Leo, the Lion, two or three degrees to its upper right.

Friday, December 19

An hour after sunset, brilliant Venus is in SW with Mars within two degrees lower right. An hour before sunup on Saturday, Moon is under hindquarters of Leo. Bright Regulus is about 14 degrees to Moon's right.

Saturday, December 20

An hour after sunset, find Venus in SW with faint Mars 1.4 degrees below. An hour before sunrise on Sunday, Moon is in SSW. Not quite to Last Quarter phase, Moon is still just over half full, and nearly halfway from Regulus in Leo to Spica in Virgo.

Sunday, December 21

Winter begins today at 3:07 p.m. EST, when the Sun stands directly over the Tropic of Capricorn in the South Pacific Ocean. From Northern hemisphere, today's midday Sun is lowest of the year, and days are shortest. In SW an hour after sunset tonight, two planets are at their closest to brilliantVenus. Faint Mars is 1.1 degrees to Venus' lower left, while bright Jupiter is within 17 degrees to Venus' upper left. All three planets get lower each evening, but at different rates. Venus will disappear in second week of January. Jupiter will sink into twilight in early February, while Mars will remain in view until March.

Monday, December 22

In the early evening, Venus and Mars are still within 1.2 degrees apart. On Tuesday an hour before sunrise, the fat crescent Moon, one-third full, is east of due south, with the first-magnitude star Spica 6 degrees to its lower left.

Tuesday, December 23

In SW at dusk, Venus and Mars are within 1.6 degrees apart. An hour before sunrise on Wednesday, the crescent Moon is in SSE. Spica is about 9 degrees to Moon's right.

Wednesday, December 24

Gleaming brilliantly in SW at nightfall on Christmas Eve, are two planets: Venus with Jupiter 17 degrees to its upper left. Using binoculars, note Mars 2.1 degrees left of Venus, and 6th-magnitude Uranus 1.6 degrees upper left of Mars. (On Friday, Mars will pass 0.6 degree lower left of Uranus.) Saturn is high, east of due south. Five planets!

Thursday, December 25

An hour before sunrise on Friday, a beautiful crescent Moon is in SE with Antares twinkling 16 degrees to its lower left. Mercury is 11 degrees to left of Antares. (Skywatchers in southern U.S. will find Antares below the Moon, and Mercury to Antares' lower left.) Mercury is getting brighter each morning.

Friday, December 26

Low in SE an hour before before sunup Saturday, the thin old crescent Moon guides us to a star and a planet: Antares 9 degrees to Moon's lower right, and Mercury about 8 degrees to Moon's lower left. This weekend, Antares-Mercury appear closest, 10-1/2 degrees apart.

Saturday, December 27

On Sunday an hour before sunrise, locate the old crescent Moon very low in ESE, about 5 or 6 degrees lower left of Mercury. Antares is 10-1/2 degrees to Mercury's right. From lower Michigan, the Moon is less than 29 hours before New.

Sunday, December 28

An hour after sunset, low in SW, the two brightest planets are now 18 degrees apart: Venus with Jupiter to its upper left. Faint Mars is 5 degrees to Venus' upper left. As sky darkens further, binoculars may show 6th-mag. Uranus 7/10 of the way from Venus toward Mars. Saturn is high in SSE, 52 degrees upper left of Jupiter.

Monday, December 29

Moon is New today at 11:56 a.m. EST. This is only date this month Moon can't be seen.

Tuesday, December 30

Face SW half an hour after sunset and enjoy the beautiful straight-line arrangement of the young crescent Moon with Venus and Jupiter to its upper left. The first sighting of this evening's slender crescent marks the start of the Islamic holy month of Ramadan, with daytime fasting beginning on Wednesday. From lower Michigan and places farther east, the Moon's age (time elapsed since New) is less than 30 hours. As the sky darkens, faint Mars appears 7 degrees to Venus' upper left.

Wednesday, December 31

Here's a splendid New Year's Eve gathering: An hour after sunset, locate the 2-day-old crescent Moon low in SW, with brilliant Venus about 5 degrees to its lower right, faint Mars about 4 degrees to its left, and bright Jupiter about 14 degrees to its upper left. Saturn is high in SSE. On New Year's morning, an hour before sunrise, Mercury and Antares are 11 degrees apart low in SE, with the star to the right of the brighter planet.

Thursday, January 1

On New Year's Day at dusk, enjoy the 3-day-old crescent Moon passing just two degrees north (upper right) of bright Jupiter. Brilliant Venus is 20 degrees to their lower right. Look every half hour until Jupiter sets, and you'll notice the Moon's motion against the background, resulting from our satellite's orbital revolution around the Earth.

Friday, January 2

In SW sky an hour after sunset, note the pleasing alignment of the crescent Moon with Jupiter and Venus to its lower right. Look for Mars midway between the two bright planets, 10 degrees from each.

Saturday, January 3

In deep twilight an hour after sunset, face east to see Orion rising, recalling opening lines of Robert Frost's poem, The Star Splitter: "You know Orion always comes up sideways. Throwing a leg up over our fence of mountains, ..."

Sunday, January 4

An hour after sunset, look high in S to see a fat crescent Moon with Saturn 8 degrees to its upper left. A telescope shows spectacular lunar surface features and Saturn's rings tipped 9 degrees from edge-on.

Monday, January 5

At sunset today, Venus appears 17 degrees to Sun's upper left. The crescent Venus is now one arc-minute across, 4 percent illuminated. It's easy to discern the crescent with a small telescope or even binoculars, if you look while the sky is still bright. An hour after sunset, locate Jupiter 22 degrees to Venus' upper left, and Saturn 6 degrees to Moon's right.


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