SKYWATCHER'S REPORT, DECEMBER 17, 1991

   Hello. This is the Smithsonian SkyWatcher's Report for the week
beginning December 17, 1991, from the Albert Einstein Planetarium at
the National Air and Space Museum.

   A bright Moon dominates the sky this week as Luna rides high
along the ecliptic plane well north of the Celestial Equator.  The
Full Long Night Moon occurs on the 21st at 5:23 AM Eastern Standard
Time, and early morning skywatchers will be treated to a small
partial eclipse of Luna's fair disk.  Between 5:00 and 6:06 AM EST
the southern limb of the Moon will graze the earth's projected
shadow, and at 5:33 AM about 9 percent of the Moon's disk will be
hidden at maximum eclipse.  For Washington area residents this all
takes place at a rather low angle in the northwestern sky, so if you
want to see it find a place where the horizon is unobstructed.  The
Moon also has one of the year's closest perigees a few hours after
the eclipse, so folks with interests along the shoreline should
prepare for unusually high tides.

   The Winter Solstice occurs on the 22nd at 3:52 AM EST, marking
the year's shortest day and the Sun's most southerly noon transit. 
From now on the days will slowly begin to lengthen and the Sun will
climb higher each day until June, when the Summer solstice will be
upon us.  Ancient Romans celebrated the Saturnalia to mark the
turnaround of old Sol's progress, and early Christians secretly used
this time of general merrymaking to observe the birthday of their
Messiah.
             Despite the fact that the solstice is still a week away, you may
have already noticed that the sun is setting later in the evening. 
Since the earth travels in an elliptical orbit around the sun, the
times of earliest sunset and latest sunrise do not correspond to the
date of the solstice.  Our earliest sunsets occurred about 10 days
ago, and by Christmas old Sol will set a full 5 minutes later than he
did last week.  Latest sunrise will occur shortly after the start of
the new year.

   Time is rapidly running out on this year's apparition of Saturn. 
He now loses about 5 minutes a day to the encroaching evening
twilight, and by the week's end he sets less than an hour after the
dusk gives way to the dark of night.  He's getting too low for useful
telescopic examination now, and he will soon be just a memory until
next Summer.

   Jupiter, on the other hand, is beginning to creep into the
nighttime sky, rising at about 11 PM at the beginning of the week. 
He comes up 4 minutes earlier each night, so that midnight revellers
on Christmas eve will be treated to his brilliant glow in the eastern
sky.  While old Jove is nowhere near Saturn in the current sky, many
scholars have speculated that a rare triple conjunction between these
two bodies may have been the star that guided the Magi to Bethlehem

   Jupiter reaches the meridian at around 5 AM now, and as he does
he's joined by another brilliant planet rising in the east.  Dazzling
Venus peeks over the horizon at around 4 AM, and as twilight begins
to gather she and Jupiter  vie for our attention.  Venus usually
wins, especially on these very cold, crisp mornings.

   There's another object in the pre-dawn sky that should not be
overlooked, though.  The fleet planet Mercury is undergoing one of
his best apparitions of the year, and he's well worth the trouble to
track down.  He has seemingly leaped up from the horizon within the
last week, and by the time of the Solstice he stands about 12 degrees
above the southeast horizon half an hour before sunrise.  He is not
terribly bright, and binoculars will help you locate him.  You may
notice three objects near the horizon if it's clear enough: Mercury
is keeping company with the ruddy star Antares and a dim planet Mars,
newly emerged from his solar conjunction.  Don't confuse them with
the red nose of Rudolph!

   So, until next week, happy planet watching, and thank you for
calling the Smithsonian.