home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Loadstar 18
/
018.d81
/
when.cont
< prev
next >
Wrap
Text File
|
2022-08-26
|
5KB
|
314 lines
When to Look for Halley - Continued
Let's take a look at the movements
of Comet Halley through our skies
during the first 120 days of the year
1986. This period will encompass
the dates between Jan 1 and Apr 30.
The program is named 'HORIZONS'
because the sky locations of Halley
are shown in relation to the southern
horizon during the times of sunrise
and sunset.
The Display Window
------------------
The display represents a window of
the sky as it would be seen by
person standing in a place where
vision is relatively unobstructed by
terrain and manmade structures. The
geographic perspective depicted is
from 40 degrees North Latitude, which
is approximated by a line connecting
Salt Lake City - Denver - Kansas City-
Indianapolis - Philadelphia.
Adjusting for Geographic Location
---------------------------------
If you live south of this line, you
can generally assume that the
positions depicted for Halley will
actually be higher in your sky at the
time shown, the farther south, the
higher above the horizon. Viewing
locations north of the line will have
poorer viewer conditions according to
the same principle.
Example: If you live 5 degrees
south of the 40 line, mentally move
the Halley location up 5 degrees
according to the vertical scale shown
to the left of the display.
Here are some reference locations
within the U.S.:
City Degrees North Latitude
---- ---------------------
Boston 42
Chicago 42
San Francisco 38
Oklahoma City 36
Los Angeles 34
Atlanta 34
Houston 30
Miami 26
Looking Up (or, NOT Looking Up)
-------------------------------
The vertical scale of the display
represents the elevation above the
horizon in degrees, where 90 degrees
is directly overhead. You will see
that Halley is mostly visible very
low on the horizon when viewed from
the Northern Hemisphere during the
observation period.
Look South, Young Man!
----------------------
The best views of the comet are to
be had from the Southern Hemisphere
from which the comet will be visible
almost directly overhead during its
peak visibility. This helps explain
why the center of the display is
looking due south. During the January
phase, the comet is speeding toward
the Sun, thus sinking into the south-
western sunsets on those cold January
evenings.
After the comet makes its solar
swing-around, it re-emerges into our
southeastern field of view, eventually
leaving us as it heads off into the
high southern skies.
Sunrise, Sunset...Fiddling on the Roof
--------------------------------------
The positions given in the display
are shown for either sunrise or sunset
on the date indicated. In the cases
of sunset viewings, the comet will
make a path toward the western
horizon after the sun has set, so
look quick! In cases of morning
viewing, the comet will be visible
during the earlier hours of the
morning before sunrise. From the
first of April on, Halley's will be
visible beginning 30 minutes earlier
each night, so that by April 13 the
comet will be visible as early as
midnight and practically gone by
sunrise.
Yes, it might just pay off to climb
up onto the rooftops for a little
comet watching! But if you take a
fiddle, try not to wake the
neighbors.
The Stuff Legends are Made of
-----------------------------
You will see a legend box in the
upper left corner of the display.
This box will show the general tail
size and orientation for Halley on
the date depicted. Also, other
special events like space probe
encounters will be depicted in the
legend box.
Making the Best of It
---------------------
In all cases, if you use a pair of
binoculars or a small telescope, you
will see much more of Comet Halley.
As a matter of fact, looking through
the lens of a 35 mm camera would im-
prove the image considerably. Of
course, if you'd stick the camera on a
tripod or a nice steady surface, you
ought to be able to get some nice
photos of the comet using a short time
exposure!
Another sure way to get a better
view is to decide that now is the time
to go down to Miami and watch the
filming of 'Miami Vice', something
you've been meaning to do, but just
keep putting off...
From May onward, Halley quickly
recedes from Earth's view as their
respective orbits carry them in oppo-
site directions. Halley will remain
visible in telescopes until mid-July.
The next time Halley is seen with the
naked eye will be in the summer of
2061, 76 years from now.
Looking Ahead
-------------
Next month we'll feed you some more
helpful info and graphics that should
make the 1986 Halley experience more
meaningful and memorable. All in all,
we are in for a time of excitement and
universal significance as we begin to
play host to our periodic visitor from
the deeps of space, Halley's Comet.
Until next month,
HAPPY COMET WATCHING!
References:
----------
"Comet-Watching", The Planetary
Report Vol.5, No.4, July-August
1985
"Looking Into Halley's Comet", The
Planetary Report, (same issue)
"Don't Miss Halley's Comet", Astronomy
Vol.13, No.10, October 1985
---------< end of article >-----------