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   One of the most powerful features in Guide is the ability to
make charts showing the paths on the earth cast during events where
one celestial object blocks out (part or all) of a second object.
This includes events such as solar eclipses,  lunar occultations of
stars and planets,  occultations of stars by planets and asteroids,
transits of Mercury and Venus in front of the Sun,  and the
(extremely rare) cases where one planet occults another.

   In this chapter,  all events of this sort will be called "eclipses",
to evade the phrase "eclipses,  occultations,  and transits".

   To show such charts,  there are a few steps you have to do first.
You need to set Guide's date and time to sometime not too long before
the actual conjunction or eclipse.  (For an example,  there have been
numerous solar eclipses.  By setting the date and time,  you tell Guide
in which event you are interested.)  Some events of this sort are listed
in Guide's "Tables" menu (see page 48).

   Next,  right-click on the objects in question.  For a solar eclipse,
for example,  you would right-click on the sun,  then on OK;  then
right-click on the moon,  and again click OK.  For an occultation of
a star by an asteroid,  you would right-click on the asteroid and
click OK,  then right-click on the star and click OK.

   Once you have done this,  the "Find Conjunction" and "Show Eclipse"
options in the Extras menu will no longer be grayed out.  Click on "Find
Conjunction",  and Guide will pause briefly while finding the nearest
(or next) conjunction of those two objects.  (From Guide's point of
view,  "conjunction" means "closest apparent approach of the objects to
each other").  It will reset the time and show you the conjunction of
those objects.

   If one of the objects is the moon,  Guide is bright enough to realize
that conjunctions occur at roughly 27-day intervals;  you can click on
"Find Conjunction" repeatedly to show subsequent conjunctions.

   Alternatively (or in addition),  you can click on "Show Eclipse".
Guide will clear the screen and switch from drawing charts of stars
to drawing charts of the earth;  you'll get a world map,  and the
path of the event in question will be shown.  (Depending on your
computer speed,  this may take a few seconds;  it is a very math-
intensive task!)
                                           
   At this point,  it may help to mention a shortcut.  The above method
for finding and showing an eclipse is wonderfully general and lets you
examine a wide variety of events. But the truth is that many people are
interested only in solar eclipses. So,  to find a solar eclipse,  all you
ever need do is to set the approximate date,  then hit the <:> (semicolon)
key.  You don't really need to right click on the Sun and Moon.


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