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7g:  Background dialog                         

   In the Background dialog in the Display menu you may modify the usual
"white stars on a black background" appearance of the screen. There are
five different types of background: "normal colors",  "chart mode",
"red mode",  "flashlight mode",  and "realistic".

   "Normal Colors" is the default;  the background is usually black.
Printouts always have black stars on white (even with color printers).
                                                           
   "Chart Mode" switches to a white background.  This was first added to
support color printing.  If you have a color printer, you can switch to                  
Chart Mode,  set colors to match what you want to see printed, and then
do a printout.  It would be very clumsy to set up colors if you didn't
have a way to turn the screen background to white. It has turned out to
have other uses, however, and some people prefer it to "normal" mode.
                                                            
   The "Red Mode" option converts everything in the chart,  and many
controls outside the chart,  to shades of red and black.  This can be
significantly less damaging to dark-adapted vision,  and is a common
choice among people running Guide in the field.  If you run Guide in
the field without using this option,  your eyes will never fully adapt
to darkness, and you won't see as much in the sky as you ought to.

   In "Flashlight mode", the background is red and markings are    
black.  The result is a bright screen that won't damage night vision.
It is sometimes useful in finding dropped eyepieces and such:  you
can switch to flashlight mode, find the missing object,  and switch
back to red mode.  Of course,  most people will use a real flashlight
with a red filter for that purpose.

   "Realistic mode" shows a bright blue sky in the daytime and a dark  
black background at night.  Between sunset and true night (when the sun
is more than 18 degrees below the horizon),  shades of blue denote the
progress of twilight.  This gives you some clue to the visibility of an
event;  if you set Guide to show,  for example,  a lunar occultation,
and the background turns bright blue,  you can reasonably expect not to
see that event.

   Finally,  there are two check-boxes for "Show Ground" and "Horizon   
Objects".  The first causes the "ground" to be shown in a solid
color. Again,  this can be useful for determining if an event is
visible;  if you turn "Show Ground" on,  and the event in question
is in the "ground" area,  you know you won't be able to see it.

   With "Horizon Objects" turned on,  Guide displays a few objects at  
the horizon such as trees,  houses,  cars,  streetlights,  and so
forth. This can provide a certain sense of scale.  It's also possible
to rearrange these objects and add new ones;  see the instructions in
the files HORIZON.DAT and OBJECTS.DAT for details. Some people

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