  unsign

  "unsign" toggles the status of the UNSIGN mode.  Warning: This is a
non-FITS standard implementation.  The FITS standard does not allow
for unsigned integer data values, but many sites write CCD images with
16 bit UNSIGNED data.  Mana looks for a FITS keyword "UNSIGN" to
determine if an image which is read in has signed or unsigned
integers.  However, since this is a non-standard concept, many sites
do not use the UNSIGN flag, yet still write unsigned data.  If the
user knows the data in the file is unsigned (ie, the user must have
apriori knowledge -- a FITS no-no!), then the user should set the
UNSIGN mode to true.  In the event that the UNSIGN mode is set, if a
FITS file is encountered which contains integers, but which does not
contain the UNSIGN keyword, Mana will make the default assumption that
the data is unsigned.  If the SIGNED mode is set, Mana will assume all
integer FITS files contain signed integers.  

((( should be able to say "unsign <buffer>" to convert the status of a
buffer to UNSIGN or to toggle the buffer's status, but not yet
implemented)))
