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considered,  though,  as you will see on the following pages.

   As you can see,  each dataset in a .TDF file starts with two lines
such as:

file !:\radio\quasars\table1.dat
title Quasars

   (The '!' stands for the CD-ROM drive letter;  it probably will be of
little use to you,  since your datasets will come from someplace else.)
These lines,  of course, simply tell Guide where to find the data and
what to call the dataset when it's listed in dialog boxes.  Each dataset
ends with the

shown 0
end

   commands (or "shown 1/end",  if the dataset is turned on).  The lines
in between,  however,  will vary widely between datasets.

   All datasets will have a description of the format of coordinates. For
example,

RA H  20   2
RA M  23   2
RA S  26   4
de d  30   3
de m  34   2
de s  37   2

   tells Guide that,  in this dataset,  the RA hours of an object is
stored in columns 20-21 of each line;  the RA minutes in columns 23-24;
and the RA seconds in columns 26-29.  Quite a few datasets will omit
the RA S,  de s, and/or de m fields,  because they use decimal degrees
or minutes;  this is not a problem for Guide.

   The following lines may also appear in a dataset description:

~dmag   40   5   # Magnitude is in columns 40 to 44
~dsizs  33   5   # Size,  in decimal seconds,  in columns 33 to 37
~dresize .5      # Multiply "size" by .5 to convert diameter to radius
~dtext   2  17   # Text for labelling this object,  in columns 2-18
~depoch 1950     # This dataset provides B1950.0 coordinates
~doffset 23040   # The actual data starts 23,040 bytes into the file
~dline size 102  # Each line in this dataset is 102 characters
~dnlines 7437    # There are 7437 lines in this dataset
~dsort 1         # The dataset is sorted in increasing RA
~dtype   4       # The dataset is shown with symbol 4 = galaxy
~dtype sc15;e0,0,32;c1;E20,20,12;E-20,-20,12;c2;m-45,0;l45,0;c14;
~dtype sc4;f3;-10,-5;10,-5;0,10;c2;
~d# Above two lines are user-created symbols

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