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   The final three values only have meaning if your "home planet" is Earth
and the "geocentric" option is not selected (i.e.,  you are observing from
the surface of the earth).  In that case,  the temperature and pressure
data are used to compute refraction,  the bending of light as it passes
through the earth's atmosphere.  All three values are used in computing
the limiting visual magnitude in Quick Info (see page 16).

8b:  Inversion Menu                 

   The Inversion Dialog is used to adapt Guide's charts to the view
seen through your telescope. It can be reached by clicking on the
compass symbol in the legend, or through the Display menu.  It shows
these options:

* Chart uninverted
  Chart inverted
  Mirror image E/W
  Mirror image N/S

  Rotation 0.0

* RA/dec (north at top)
  Alt/az (zenith up)
  Ecliptic north up
  Galactic north up

   The first four radio buttons let you flip the chart top to bottom,
left to right,  or both.
                               
   "Chart uninverted" says that the chart is oriented as you would see   
it without a telescope. In your telescope, however, you might see
something different.  Many telescopes use mirrors, so you might see a
mirror image. Lenses often spin the image 180 degrees: most refractors
invert the image totally.  So do Cassegrain telescopes, like the
popular "SCT" (Schmidt- Cassegrain) telescopes.  Coude telescopes will
invert only on one axis.

   The next line states "Rotation 0"; you can use this to add any  
arbitrary rotation you want.  People with unusual telescopes might
want to add a final "spin" of 20 degrees to their charts,  for example.
                                                       
   The next item tells you that North is up (i.e.,  at the top of the
screen).  So what?  Isn't North always up on a chart?  Well, not quite.

   What Guide is telling you is that celestial North (the direction to
the North Pole) is at the top of the chart.  Most star atlases are
printed that way. However, as the earth turns, the sky seems to turn.
Thus,  the Big Dipper, which seems to be "right side up" when it's
close to the northern horizon, looks "upside down" when you see it high
in the sky. You would usually turn a paper star chart until it looks

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