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MAKEPLAN.DOC
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1993-03-23
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MAKEPLAN V1.3 - a STARPLOT Utility.
INTRODUCTION
This program can make a STARPLOT compatible file containing Sun, Moon and
Planet positions for any year between 1890 and 2090. It can also, given
the orbitel elements, create similar files with comet or minor planet
positions.
To start the program, in the directory containing the three files
MAKEPLAN.EXE, PLANETS.NDX and PLANETS.DAT simply type;
MAKEPLAN
The rest of this document gives further details on MAKEPLAN.
On typing MAKEPLAN you will be presented with a copyright title screen,
press any key to get past this and you will see a menu screen with the
choices of Sun, Moon and Planets, or Minor Planets or Comets.
SUN, MOON and PLANETS
On choosing Sun, Moon and planets you will be presented with a setup screen
with default parameters.
Use the tab key to move about the parameters, context sensitive help will
be displayed as you do so.
The parameters are:
Year - this is the year over which the positions are calculated, you can
change it to any value between 1890 and 2090.
Filename - this is the file to which the results are saved. It is a
STARPLOT compatible file, typically "PLAN1992.STR". You can change the
name to any valid DOS filename.
Dates - for each of the planets, and for the sun and moon, there is a field
containing the days of the month on which the position of the body will be
calculated. Pressing the space bar toggles these values to one of the
following possible sets of dates:
None - No positions for this body will be calculated.
1st and 15th - The position of the body will be calculated for the
first and the fifteenth day of each month.
1st,11th,21st
1st,8th,15th,23rd
1st,4th,7th,10th....
For example, if you set every body to "None" apart from mars, which you set
at "1st,8th,15th,23rd" you would end up with a file containing only
positions for mars. 48 positions would be calculated, four for each of the
twelve months of the year. You could load it into STARPLOT, thus showing
all the 48 positions on the screen, which would trace out the planets path
for you, or you could use the "Planet File Merge" option to pick a single
position of mars out on any given day.
Even though the file only contains four positions a month, the Planet File
Merge can still find intermediate days, since it uses the positions it does
have to interpolate for those days not in the file.
This is a reason why for the faster moving bodies such as mercury and
especially the moon, you should choose to calculate more positions, whereas
for the slower bodies such as neptune and pluto, the "1st and 15th" will be
good enough since the motion being small, is easily interpolated for
intermediate days.
Having set the parameters, choose 'Execute Calculation' to begin the
calculation. As the values are calculated they are put into the file and
are displayed on screen. If you are calculating a lot of positions for all
the planets this could be a lengthy process, particularly if you have a
slow PC. If this is the case then you might as well go have a cup of tea
and come back later.
When finished the program returns to the setup screen allowing you to
either return to the top menu or start another calculation. If you do
another be sure to change the filename!
MINOR PLANETS
To successfully create the minor planets path you will need its orbitel
elements, these are published by astronomical clubs and institutions. In
particular your library should have a copy of The Astronomical Almanac
which lists the elements for the larger minor planets. The setup screen
allows you to input the elements, and also gives a brief description of
each element as you do so.
On choosing 'Execute Calculation' a STARPLOT compatible file will be
created, containing the positions calculated over a six month period on the
1st, 4th, 7th, 10th, 13th, 16th, 19th, 22nd, 25th and 28th of each month.
The magnitude parameters H and G for some of the minor planets are:
H G
Ceres 3.32 0.11
Pallas 4.13 0.15
Juno 5.31 0.30
Vesta 3.16 0.34
Astraea 6.91 0.25
COMETS
The comets set up screen and action is very similar to that of minor
planets. The orbitel elements are slightly different to allow for the
possibility of a comets orbit being parabolic, whereas a minor planets
is always elliptical. The magnitude parameters are also different.
THE CALCULATION
The calculations follow the techniques given in the book "Astronomical
Algorithms" by Jean Meeus. The software toolbox associated with the book
has been used, MAKEPLAN therefore includes routines written by J Sax, a
condition of using this software is the display of the copyright notice
which appears on using the program.
MAKEPLAN uses two data files, PLANETS.DAT and PLANETS.NDX which must be
present in the same directory.
Geocentric positions are calculated at the required intervals through the
year. Then apparent positions are recalculated taking light time into
account.
Aberration and nutation effects are not included. This is because the
resultant file is to be plotted on a star chart, and aberration/nutation
has the same effect on background stars as on the planets position.
Finally precession is taken into account, the coordinates are transformed
to the equinox of J2000.0, so the body can be plotted directly on a star
chart drawn to that epoch.
Magnitudes are also calculated. The value 0.0 is given as the Suns
magnitude, which is just a default value of no meaning.
For the Moon, the value inserted here is the phase - between 1.0 and 0.0,
it is unfortunate this is labelled Magnitude in the STARPLOT program, but
otherwise the field would not be used at all, and it might as well hold
phase information rather than nothing.
MAKEPLAN can be freely used, copied and passed on. If you haven't already
done so, please register your copy of STARPLOT.
If you find any bugs let me know!
- Bernard Czenkusz