mpc_area.txt

Clicking on the listing of MPC codes at the bottom of the screen brings
up a small dialog of options.

First,  you can select between three ways of displaying MPC codes :
just the code for the currently selected observation;  or "some"
codes (the default,  just enough codes to usually list the major
observers and those for observations currently on screen);  or
"all MPC codes" (really,  all those that will fit in the screen area;
if there are enough observatories involved,  Find_Orb can't fit all
of them at once.)

Next,  you can find the preceding/following observation from whichever
MPC code you clicked on.  This helps if you can see from the MPC code
listing that observations were made from (XYZ),  but none of them
are currently on screen.

If there are so many observatories that they don't all fit,  the
"Find obs from a given code" option can help.  It will provide a
compact dialog with just the MPC codes showing;  click on one,  and
the next observation from that code will be found.