[find_orb] Various updates

[Bill Gray]

Hello all,

    Several minor updates since my last posting in March... actually, 
quite a few;  my apologies for the length of this post.  I should just 
make smaller updates more frequently.  On the bright side,  there's a 
lot of good stuff here;  I encourage upgrading :

    -- The program is now somewhat better about puzzling out an initial 
orbit on its own.  That mostly involved improvements in outlier 
rejection.  I've been focussing on this problem in recent months; 
ideally,  Find_Orb could be used in a fully automatic mode in which it 
would read in files of astrometric data and spit out orbits unattended. 
  It's actually rather close to that,  with the occasional "gotcha" that 
I'm still working on.

    -- You can specify data about your MPC code,  such as primary and 
secondary mirror size,  sky brightness at zenith,  and pointing limits 
(such as an irregular horizon and/or declination limits).  These will be 
used in ephemeris generation to compute somewhat accurate expected SNRs 
and exposure durations,  and so that the ephemerides will tell you when 
an object is below your "real" horizon,  rather than just below altitude 
0 degrees.  See the file 'site_310.txt' for an example and discussion of 
how to set this up.

    -- User interface improvements,  mostly involving the mouse.  See 
https://www.projectpluto.com/findhist.htm#user_interf for details.

    -- In ephemeris generation,  if you click on the ephemeris type (by 
default,  "Observables"),  you get a menu of possible ephemeris types. 
The "State vectors" and "Cartesian coord positions" options now also 
provide options for specifying distance and time units and selecting 
equatorial vs. ecliptic coordinate systems.

    -- Also in ephemeris generation : if you toggle 'Show Advanced 
Options' on,  you'll see that one of them is 'Show explanations at end 
of ephems'.  These explanations will be shown for the ephemeris 
quantities you've turned on,  and will appear after the ephems and in 
any pseudo-MPECs you generate.

    -- Added a four-parameter comet non-grav model,  with a parameter 
reflecting a time lag between perihelion and maximum activity.  See 
https://www.projectpluto.com/findhist.htm#comet_dt for details.  Usual 
warning : don't apply non-gravs unless you really have reason to think 
the object is cometary or small enough for SRP to matter.

    -- You can now specify ephemerides to be from the "MPC codes" SE1 
through SE5, corresponding to the Sun-Earth Lagrange 1 through 5 points. 
  Similarly,  EM1 through EM5 are the Lagrange points for the Earth-Moon 
system,  and SJ1-5 for the Sun-Jupiter pair.  There are further comments 
on all this at https://www.projectpluto.com/findhist.htm#lagrange.

    -- Magnitude band offsets now use the MPC-blessed table,  so H 
values should be a little closer to MPC's values.

    -- Lots of minor bug fixes,  and updates to MPC codes and such.

-- Bill