SKYWATCHER'S DIARY: December 1997
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
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
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
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
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
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
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
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
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
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
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
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