   Version date: 2018 Feb 22

   The parameters shown in this software are basically the same as those
shown in the Windows software,  as described at

https://www.projectpluto.com/find_orb.htm

   Commands are very different,  because they are all keyboard based (but
you can do a few minor things with the mouse;  see end of this text.)

?      (Or any other unrecognized key) Shows this file (dos_help.txt).

   ORBIT-FITTING COMMANDS:

r      Reset R1 and R2,  for use in the method of Herget.  Results in being
       prompted to type in new values for both.  By default, units are AU,
       but one can append 'km';  e.g.,  '.01 500000km' or '10000km 20000km'
       are interpreted logically.  Enter one value,  and R1=R2 is assumed.
e      Reset the epoch.  Results in being prompted to enter a new epoch.
       This can be simply a JD ("2451000.5") or a year/month/day ("2004
       10 2").  Or you can enter,  say,  "+20" to advance the epoch 20
       days,  or "-40" to set it back 40 days,  etc.  Or "now" to set the
       epoch to today,  or "now-7" to set it to a week ago.
v      Find Va'isa'la' orbit.  You'll be prompted to enter a perihelion
         (or aphelion) distance;  it will then find a 'best fit' orbit with
         that apsis distance at the center of the arc.
l      Set a Limited orbit (e.g,  "e=.1",  "q=12.4",  "a=2.3,e=.15").
h      Take one step using the method of Herget.
f      Take one "full step" using the method of least squares.
g      Determine orbit with method of Gauss.  (There may be alternative
         solutions;  hit 'g' again to cycle through them.)
|      Determine a Monte Carlo variant orbit.  Find_Orb will continue
         generating variants until you hit another key to stop it.  Observe
         the changes in the orbital elements,  and you get an idea of the
         level of uncertainty.  (Elements will also be stored in 'mpcorb.dat'.)
:      'Linearizes' the orbit,  as described at:
         https://www.projectpluto.com/vaisala.htm#linearized
#      Uses a downhill simplex method,  as described at
         https://www.projectpluto.com/herget.htm#simplex
/      Uses a downhill 'superplex' method,  as described at the above URL.
Backspace   Undo the last orbit-fitting command.
F12    Find a circular orbit connecting the first and last positions.  Hit
         this repeatedly,  and Find_Orb will iterate through possible
         solutions.  If the arc is long enough,  there may be multiple-orbit
         solutions,  including many spurious retrograde ones.  (Or there may
         be no circular orbits at all.)

   INTEGRATION MODEL COMMANDS (perturbers, non-grav effects):

1...9  Toggle inclusion of Mercury...Pluto as a perturbing object.
0      Toggle inclusion of the Moon as a perturbing object.
!      If all perturbers are off,  turns main planets on; otherwise,
            shuts off all perturbers at once.
a      Toggle inclusion of up to 300 asteroids.  (See documentation for
         details,  including on how to limit/increase asteroid use.)  NOTE
         that this can slow things down a bit and appears to rarely matter.
*      Toggle inclusion of the effects of solar radiation pressure (SRP).
         Turn this on,  and on the next "full step",  Find_Orb will do a
         _seven_-parameter fit,  with the area/mass ratio solved for as an
         added variable.
^      Toggle on comet parameters A1 and A2.  Turn this on,  and on the next
         'full step',  Find_Orb will do an _eight_-parameter fit,  with A1
         and A2 solved for as added variables.  Hit it again,  and A3 will be
         included for a nine-parameter fit.  Yet again,  and you're back to
         not using comet parameters (i.e.,  a three-way cycle).

      OBSERVATION TOGGLING/WEIGHTING/SEARCHING:

F1 or Alt-U
       Toggle all observations prior to the currently-selected one.
F2     Toggle all observations after the currently-selected one.
F3     Toggle all observations for the currently-selected observatory.  This
         lets you,  say,  "shut off all 703 observations."
F4     Find previous observation from the current observatory.
F5     Find following observation from the current observatory.  Both of these
         functions wrap around at the start/end of the list of observations.
F6     Find preceding excluded observation.
F7     Find following excluded observation.  Again,  these both wrap around.
Shift-F8   Enter a three-character MPC code,  and the next observation made
           from that code will be searched for.  Or,  enter a date/time and
           the first observation made after that date/time will be sought.
F9     Find the first included observation in the arc.
F10    Find the last included observation in the arc.
%      Reset uncertainty of a particular observation.  Enter,  e.g.,  '.3'
            to reset the positional uncertainty to 0.3 arcseconds;  'm.2'
            to reset the photometric uncertainty to 0.2 magnitudes;  or
            't4' to reset the uncertainty in timing to four seconds.

            ON-SCREEN DISPLAY:

p      Show orbital elements with an extra digit of precision.
P      Show orbital elements with one less digit of precision.
Shift-F7    Toggle between the 'pure' MPC-formatted eight-line elements,  with
         P and Q vectors;  and Find_Orb's slightly revised format,  with
         uncertainties (if available),  P and Q,  and extra MOID data.
+      Choose center object for orbital elements.  By default,  Find_Orb
         determines the planet with the greatest influence on the object (at
         the time of epoch) and the elements are relative to that object,  so
         you can get geocentric,  Jovicentric,  etc. elements.  Use '+' to
         a particular central object (which can be the barycenter of the
         solar system).
i      Toggles the 'information' about the currently-selected observation
         (reference,  observing station,  magnitude/motion of the object).
         This data takes up three lines;  when shut off,  three more lines
         of residuals are shown.
j      Toggles the two lines showing which perturbers are included,  R1 and R2,
         orbital restrictions,  and the step size.  When shut off,  two
         more lines of residuals are shown.
o      Toggles display of the orbital elements.  You normally wouldn't want
         to shut them off,  but if you do,  ten more lines of residuals are
         shown.  Combine with the above 'i' and 'j' commands,  and you can
         get a full-screen display of observations/residuals.
;      Toggles display of the "residual legend",  which explains what the
         assorted data in the residual area mean.
c      (WATCOM-compiled under DOS version only) Select a different text
         mode from the default 80x25 one.  Modes include 100x50, 132x60,
         etc.  Not all modes may work with your video card.
-      Cycles display of the list of observatories among three options:
         just data for the observatory for the currently-selected observation;
         use about a third of the observation area for observatory data;
         or use most of that area for observatory data.

        RESIDUAL-RELATED COMMANDS:

Cursor keys :  move up/down one observation,  or a "page" up/down
       at a time;  'Home' to first obs, 'End' to last.
-      Toggles display of the list of observatory codes.
x      Toggle the inclusion of the currently selected observation.
{      Filter all observations according to residual level.
}      Cycles between 'normal' residuals (given to 0.01 arcsec precision),
         'precise' residuals (0.001 arcsec precision),  and 'super-precise'
         residuals (values under a milliarcsecond are shown as micro, nano,
         pico,  etc.)  No one will normally use this;  I did so to verify
         the level of roundoff/integration error in the software.
k      Cycle from long residual format to short (such as MPC uses),  to
         showing the original 80-byte observation record,  back to the
         long residual format.
b      When in "usual" one-obs-per-line residual formats,  toggles
         between decimal day display and HH:MM:SS display.
d      Show resiDuals in current format & save to file 'residual.txt'
t      Toggle between "usual" residuals in RA and dec,  and residuals in
       time and cross-track distance.
=      Toggle between "usual" residuals,  and display of total angular
       residual and magnitude residuals.
w      Find Worst (highest-residuals) observation.
@      Toggle off display of residuals outside the currently-used arc
         of observations.  By default,  Find_Orb will compute those
         residuals;  if the observations are quite far from the actually
         used arc,  that can take a while.  Toggling them off can help
         speed things up a bit.
(     Compute residuals for _all_ observations.  By default,  the Herget,
         Vaisala, and Gauss methods don't bother computing residuals for
         observations not within the currently-set arc.  This speeds up
         the program,  but does require you to hit this key if,  for some
         reason,  you want to know those residuals.
]     Toggles display of 'deltas':  except in the short MPC format,
         differences between the currently-selected observation and
         the others,  in time,  RA, and dec,  will be shown.  Useful
         to get a quick how-far-is-this- obs-from-that-one, in time or
         position.

      EPHEMERIS-RELATED COMMANDS:

m      Make an ephemeris.  You get a menu asking for a starting date/time,
          step size,  and number of steps.  You can also set the observing
          location (by MPC code) and have a little control over what
          ends up in the ephemeris  Ephemeris-specific help is available
          from within this menu.

   MISCELLANEOUS COMMANDS:

)      Show a user-selected text file.  I added this because I'm sometimes
         in the midst of solving an object and would like to look at some
         file or another,  without needing to exit or start a new console.
n      Select a different object from the input file of astrometry.
`      (that's a backward-quote-mark!) Toggles between N(uclear) and T(otal)
         comet magnitudes.  When a full-step is done,  you'll see that
         'M(N)' becomes 'M(T)',  or vice versa.
s      Save orbital elements to a file.  (Whatever elements are shown
         on-screen are also stored in the file 'elements.txt'.  This
         command really just copies 'elements.txt' to a file of your choice.)
[      Show covariance and correlation matrices from last 'full step',
         plus an attempt to extract the largest eigenvalue of the former
         in hopes of computing uncertainty info. This data is stored in
         the file 'covar.txt';  this command really just displays that file.
q      Exit the program

   COMMANDS NOBODY SHOULD HAVE TO USE (mostly for my testing purposes,  or
         not really working yet)

z      Reset the integration step size,  in days.  (No longer relevant,
         except when using the testing-only symplectic integrator.)
$      Reset integration tolerance (default is 1e-11).  Used for testing
         how good the integrator is.
y      Show details of the last Gauss orbit computation.
z      Integrate current orbit forward,  then back,  a certain number of
         days,  and compare to original result.  Used when I suspect the
         integrator's not quite as precise as it might be,  and to evaluate
         what integration tolerance should be used.
"      Shows details of Curses mouse commands (these differ from one platform
         to the next,  and I needed a way to puzzle them out),  and info on
         the DE file currently in use.
.      Show flavor of Curses and DE version in use.
,      Show 'debug.txt' (log of debug messages).
\      Shift all observations from a given observatory by a given time offset.
         Used when I was trying to puzzle out some timing errors from a
         specific observatory for a specific object.
Alt-D  Reset debug level.
Shift-F6   Reset atmospheric drag (doesn't work yet)
&      Attempt to find precoveries within a list of plates (doesn't work yet)

Mouse actions:

   Click on any of the "menu" items on the top line to get that action
   Click on the R1, R2 display to be prompted to enter a new R1 and R2
   Click on a planet abbreviation to toggle its use as a perturber
   Click on an observation to select it;  double-click it to toggle it
   Click on the "residual legend" to cycle the residual format
   Click on the epoch to enter a new epoch.
   Click on the list of observatories to toggle that list.  The observatory
      for the current observation will always be listed.
   Click on scroll bar at right edge (in 'help',  or in ephemerides,  or
      next to the observations in the main screen) to... well... scroll.
   Turning a mouse wheel may scroll within the list of residuals or within
      the file you're looking at (depends on the platform;  mouse support
      is a little sketchy in some flavors of Curses.)

The following table was shamelessly copied from:

http://www.minorplanetcenter.net/iau/lists/Sizes.html

It lists the diameters of minor planets corresponding to the given values of
the absolute magnitude, H.  The diameter is to be read as kilometers when H
is in the "H(km)" column,  meters in the "H(m)" column,  and millimeters in
the "H(mm)" column.  For example, H = 8.0 corresponds to a diameter of 65 to
150 km, whereas H = 23.0 corresponds to a diameter of 65 to 150 m.

Conversion of H to a diameter for a specific object requires knowledge of
the object's albedo.  This quantity is not known for most objects, so the
diameters listed here are given for albedoes of 0.50,  0.25,  and 0.05.
Most objects have albedos in this range.  If a specific object has an
albedo less than 0.05, the diameter will be larger than the upper limit
listed here (possibly up to infinity,  if you imagine an extremely black
"Stealth Asteroid").  If the albedo is greater than 0.50, the diameter will
be smaller than the lower limit given here (possibly as low as sqrt(.5) of
that lower limit,  if the object is icy and has essentially a 100%
albedo... but no lower than that;  you can't reflect more than 100%.)

      Table: Probable diameter ranges for various
              H values and albedo values.

           H(km)          Albedo          H(m)   H(mm)
                   0.50    0.25    0.05
           -2.0    4700 -  6700 - 14900    13.0  28.0
           -1.5    3700 -  5300 - 11800    13.5  28.5
           -1.0    3000 -  4200 -  9400    14.0  29.0
           -0.5    2400 -  3300 -  7500    14.5  29.5
            0.0    1900 -  2600 -  5900    15.0  30.0
            0.5    1500 -  2100 -  4700    15.5  30.5
            1.0    1200 -  1700 -  3700    16.0  31.0
            1.5     940 -  1300 -  3000    16.5  31.5
            2.0     750 -  1050 -  2400    17.0  32.0
            2.5     590 -   840 -  1900    17.5  32.5
            3.0     470 -   670 -  1500    18.0  33.0
            3.5     370 -   530 -  1200    18.5  33.5
            4.0     300 -   420 -   940    19.0  34.0
            4.5     240 -   330 -   740    19.5  34.5
            5.0     190 -   260 -   590    20.0  35.0
            5.5     150 -   210 -   470    20.5  35.5
            6.0     120 -   170 -   370    21.0  36.0
            6.5      95 -   130 -   300    21.5  36.5
            7.0      75 -   110 -   240    22.0  37.0
            7.5      60 -    85 -   190    22.5  37.5
            8.0      45 -    65 -   150    23.0  38.0
            8.5      40 -    50 -   120    23.5  38.5
            9.0      30 -    40 -    95    24.0  39.0
            9.5      25 -    35 -    75    24.5  39.5
           10.0      19 -    25 -    60    25.0  40.0
           10.5      15 -    20 -    50    25.5  40.5
           11.0      12 -    17 -    37    26.0  41.0
           11.5       9 -    13 -    30    26.5  41.5
           12.0       7 -    11 -    24    27.0  42.0
           12.5       6 -     8 -    19    27.5  42.5
           13.0       5 -     7 -    15    28.0  43.0
           13.5       4 -     5 -    12    28.5  43.5
           14.0       3 -     4 -     9    29.0  44.0
           14.5       2 -     3 -     7    29.5  44.5
           15.0       2 -     3 -     6    30.0  45.0
           15.5       1 -     2 -     5    30.5  45.5
           16.0       1 -     2 -     4    31.0  46.0
           16.5       1 -     1 -     3    31.5  46.5
           17.0       1 -     1 -     2    32.0  47.0
           17.5       1 -     1 -     2    32.5  47.5

   Important note:  residuals are O-C ("observed minus computed"),  so
positive y residuals mean the object was observed to be _north_ of
prediction, positive x _east_ of prediction.

New moon dates for the next few years :

2016 May  6     2017 Dec 18     2019 Aug  1     2021 Mar 13     2022 Oct 25
2016 Jun  5     2018 Jan 17     2019 Aug 30     2021 Apr 12     2022 Nov 23
2016 Jul  4     2018 Feb 15     2019 Sep 28     2021 May 11     2022 Dec 23
2016 Aug  2     2018 Mar 17     2019 Oct 28     2021 Jun 10     2023 Jan 21
2016 Sep  1     2018 Apr 16     2019 Nov 26     2021 Jul 10     2023 Feb 20
2016 Oct  1     2018 May 15     2019 Dec 26     2021 Aug  8     2023 Mar 21
2016 Oct 30     2018 Jun 13     2020 Jan 24     2021 Sep  7     2023 Apr 20
2016 Nov 29     2018 Jul 13     2020 Feb 23     2021 Oct  6     2023 May 19
2016 Dec 29     2018 Aug 11     2020 Mar 24     2021 Nov  4     2023 Jun 18
2017 Jan 28     2018 Sep  9     2020 Apr 23     2021 Dec  4     2023 Jul 17
2017 Feb 26     2018 Oct  9     2020 May 22     2022 Jan  2     2023 Aug 16
2017 Mar 28     2018 Nov  7     2020 Jun 21     2022 Feb  1     2023 Sep 15
2017 Apr 26     2018 Dec  7     2020 Jul 20     2022 Mar  2     2023 Oct 14
2017 May 25     2019 Jan  6     2020 Aug 19     2022 Apr  1     2023 Nov 13
2017 Jun 24     2019 Feb  4     2020 Sep 17     2022 Apr 30     2023 Dec 12
2017 Jul 23     2019 Mar  6     2020 Oct 16     2022 May 30     2024 Jan 11
2017 Aug 21     2019 Apr  5     2020 Nov 15     2022 Jun 29     2024 Feb  9
2017 Sep 20     2019 May  4     2020 Dec 14     2022 Jul 28     2024 Mar 10
2017 Oct 19     2019 Jun  3     2021 Jan 13     2022 Aug 27     2024 Apr  8
2017 Nov 18     2019 Jul  2     2021 Feb 11     2022 Sep 25     2024 May  8
