SKYWATCHER'S REPORT, DECEMBER 3, 1991

   Hello. This is the Smithsonian SkyWatcher's Report for the week
beginning December 3, 1991, from the Albert Einstein Planetarium at
the National Air and Space Museum.

   The Moon returns to the early evening sky by the week's end, with
New Moon occurring on the 5th at 10:56 PM Eastern Standard Time. 
You'll probably have some difficulty spotting the thin waxing
crescent over the weekend, but by the evening of the 9th she should
be easy to see just northwest of yellowish Saturn.

   This week marks the times of the year's earliest sunsets, as old
Sol dips below our southwestern horizon at about 4:46 PM.  Sunset
begins to creep back to a later time in about ten days, but the time
of sunrise is still progressing later in the morning.  On the day of
the Winter Solstice we will experience the shortest amount of
daylight, but sunset will be some 5 minutes later than it is this
week.  The latest sunrises occur in early January, but by then we
will really notice the difference in the time of sunset.  This all
comes about due to a number of circumstances, but it mostly has to do
with the fact that the earth's orbit is not circular about the Sun,
but rather an ellipse.  The earth travels at different speeds in its
orbit depending on the time of year, and this affects the time when
we see sunrises and sunsets.  So enjoy the stars this week; you have
the most time in the evening for skywatching right now.

   Saturn is still visible in the southwestern sky, setting about 2
hours after the end of evening twilight.  He lies a few degrees
southwest of the young crescent Moon on the 9th, but on other nights
you can still use the stars Vega and Altair to find him.  He's
getting pretty low for telescopic examination now, but you might
still want to give him a look.  His rings are still tipped about 20
degrees to our line of sight, but they are starting to close up now. 
We won't see them this wide again until early 1999.

   The absence of the Moon and the early end of evening twilight
make this the perfect time of year to go out and learn some
constellation patterns.  The sky through the night is dominated by
three very prominent geometrical patterns, each indicative of a
particular season.  First off is the Summer Triangle, visible in the
west as twilight ends.  This group is made up of the aforementioned
Vega and Altair, with slightly dimmer Deneb bringing up the rear. 
Deneb is nearly overhead in the early evening, but it quickly heels
over in the west as the night wears on.

   By 9 PM the Triangle has given way to the Great Square of
Pegasus, which lies just a bit south of the zenith.  Pegasus forms a
nearly perfect square, and while its stars are not particularly
bright, its shape is very distinct.  Initially the interior of the
square looks completely blank, but sooner or later you'll pick out a
few stars.  3 or 4 may be seen from near the city, but up to 20 are
visible when you get away from the urban sprawl.

   By midnight the sky is ablaze with stars as mighty Orion leads
the parade of the Great Winter Circle up from the horizon.  Moving
clockwise from Rigel, the left knee of Orion, we pass Sirius,
Procyon, Pollux, Castor, Capella, and Aldebaran in a vast oval that
encompasses 9 of the 25 brightest stars in the night.  

   As the Circle climbs higher, look to the east for the rising
planet Jupiter, which should become visible shortly after midnight. 
Old Jove is moving rapidly into the evening sky now, rising about 4
minutes earlier each night.

   Just a few short weeks ago Jupiter and Venus were together in the
pre-dawn sky.  Now there's almost 4 hours of time between their
respective risings, and Venus alone heralds the coming of another
dawn.  She's at her best about an hour before sunrise.

   So, until next week, keep looking up, and thank you for calling
the Smithsonian.