gap, sub_array
Change the time gap used to delimit neighboring scans.
EXAMPLES
--------

1. To assign a 30 minute scan separator to all sub-arrays:

   0>scangap 30*60
   Delimiting interscan gap changed to 1800 seconds in all sub-arrays.
   0>

2. To re-instate the default (1 hour) separator:

   0>scangap 0     
   Delimiting interscan gap changed to 3600 seconds in all sub-arrays.
   0>

3. To assign a 20 minute scan separator only to sub-array 2:

   0>scangap 20*60, 2
   Delimiting interscan gap changed to 1200 seconds in sub-array 2.
   0>

4. To see what the current gaps are set to, omit all arguments:

   0>scangap
   The delimiting interscan gap is 3600 seconds in sub-array 1.
   The delimiting interscan gap is 1200 seconds in sub-array 2.
   0>

PARAMETERS
----------

gap        -   The new interscan gap to assume. This is the minimum
               time separation between neighboring integrations at which
               integrations are taken to occupy different scans.
               When an observation is first read into difmap, all
               sub-arrays are assigned a scan delimiter of 3600
               seconds (1 hour). This default may be re-selected by
               giving 'gap' as 0, as in the second example above.

sub_array  -   Optional: Default=0
               If this argument is not provided, or is given as 0,
               then the new scan delimiter is assigned to all
               sub-arrays. Otherwise, the number given specifies the
               sub-array to which the scan separator should be
               assigned.

CONTEXT
-------
All difmap plotting commands that plot anything versus time, offer
the option of resolving the data into multiple isolated scans. These
scans are then plotted side by side with the intervening gaps removed.
The plotting commands also know not to extend model lines between
scans, even when scan mode is not in effect.

In order to decide what constitutes a scan, difmap simply says that
any two integrations that are separated by more than a given amount of
time mark the end of one scan and the start of a new scan. By default
this time interval is one hour, and is a good choice for most
observations. Somethines the default is not the correct choice, and
the 'scangap' command gives you the opportunity to change the default,
either on a sub-array by sub-array basis, or globally for all
sub-arrays.

Note that no more than 20 scans per sub-array are allowed. This means
that if too short an interval is requested, the command will emit an
error message ignore the requested interval.

RELATED COMMANDS
----------------
vplot    -   Display observed and model visibilities from the current IF.
tplot    -   Display the time-sampling of each telescope of the current IF.
corplot  -   Display the self-cal corrections of the current IF.
cpplot   -   Display observed and model closure phases interactively.