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   In fact,  the .TLEs provided with Guide will already be somewhat
out of date by the time you get this CD.  You might be able to get,
say, an approximate time at which ISS will pass overhead. But getting
current data is a good idea.

   When you click on the "TLE=" option,  you'll see some information
about sites where you can get satellite elements,  with links provided.
In most cases,  you can simply click on an option to download data for
all satellites,  or for a specific group of satellites.

   The Projections submenu offers a long list of chart projections:   
stereographic (the default),  orthographic,  gnomonic,  Mercator,
and more.  Each serves a different purpose.

   Stereographic projection preserves the shapes of objects quite well,
no matter how large an area is being shown. At Level 1 (180 degree field
of view),  the other projections will show very distorted constellations
near the edge of the chart.  Stereographic projection results in
exaggerated sizes of objects near the edge, but their shapes are okay.
Therefore stereographic projection is used for "all sky" charts in the
center of many astronomy magazines.

   Orthographic projection is best suited for terrestrial maps,  not
celestial charts. In terrestrial maps, one gets an "Earth-from-space"
sort of view.  You may want to use it when displaying
eclipse/occultation paths on the Earth.

   Gnomonic projection involves horrible distortion at large fields
of view.  However,  it shows great-circle routes as straight lines.
It is therefore useful for meteor observers;  draw the paths of meteors
on this chart,  and they will appear as straight lines emerging from
a single point (the radiant).

   Equidistant projection is true in distances and azimuths from the center
of the chart.  It is mostly used for terrestrial charts; short-wave radio
amateurs like its use.

   The Mercator,  Peters,  Miller,  and "simple" projections are almost
never used for sky charts.  They are all cylindrical projections,  in
which lines of latitude are projected as parallel horizontal lines and
lines of longitude are projected as parallel vertical lines.  (For a
sky chart,  read "lines of declination and RA",  or in alt/az coordinates,
"lines of altitude and azimuth.")  The price for this is that the north
and south poles (for sky charts,  read "near the celestial poles") become
extremely distorted.  This isn't such a big deal for charts of the earth,
where people are not too concerned about the poles.  But people look at
the celestial poles all the time.

   The Mercator projection preserves shapes.  But areas are greatly
magnified near the poles.  The Peters projection has the reverse problem:

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