Overview of BoPlanets

BoPlanets is a virtual planetarium, which shows the positions of the planets in the sun system relative to an observing planet, which can be selected out of the planets and the sun. The planets can be shown in various views. In the ecliptic view the Cartesian coordinates, in the equatorial view right ascension and declination, in the horizontal view azimuth and altitude of the planets relative to an observing planet are displayed. In the horizontal view the position of the observer on the observing planet can be selected out of a list of locations or directly by its longitude and latitude.

A list of rise, transit and set times of a planet, as seen by an observer on the observing planet, may be generated. Times were given as GMT date&time or as local date&times at the observer's location on the observing planet.

You may have a look to the epicycles of the planets, when the earth was seen as the centre of the planet system. Or you may observe the course of the sun as seen from the mercury, where the sun seems to go backwards and then forwards again. You may change some of the orbital parameters to see the effect on the orbital of the planet.

You can let the planets moving by single steps or let them run continuously. You may vary the step size to let the planets run faster or you can ask for the static and dynamic orbital parameters of a planet.

If there are questions, suggestions or bugs in the software then do not hesitate to email to

You may download new releases from:

Starting BoPlanets

BoPlanets requires Java run time environment release jre1.6 or above. Download the actual release from:
http://www.oracle.com/technetwork/java/javase/downloads
and install it in <java install dir>.
Add the following path to the system environment variable "path":
  • <java install dir>/bin

Extract the downloaded zip file to an installation directory.

  • Open a DOS window and navigate to the installation directory. BoPlanets will be started by:
    java -jar BoPlanets.jar

The form Select Planets will appear. Select the observing planet, from which the other planets should be observed. Choose the planets to be observed.  Clicking the start button will open the main form with the logarithmic ecliptic view of the planets.

Elements of the Main Form

The main form consists of the following elements:
  • a menu bar with the menus File, Views, Options, Orbital Parameters, Rise&Transit&Set and Help
  • the images of the selected planets and at the last position the observer
  • a control panel
  • the drawing panel showing the movement of the planets in different views

Menu Views

The menu Views contains the following menu items:
  • Ecliptical View: shows the planets at their Cartesian coordinates of the ecliptic system
  • Logarithmic Ecliptical View: as Ecliptical View, but with logarithmic scaling of the radius vector
  • Equatorial View: shows the planets in the equatorial plan of the observer with right ascension and declination of the planet above the equatorial plane
  • Horizontal View: shows the planets in the horizontal system of an observer on the observing planet. The location of an observer is given by geographical longitude and latitude.
  • Location (if Horizontal View is selected): select the location of the observer on the observing planet

Menu Options

The menu Options consists of menu items by which the actual view may be modified.
  • in ecliptical (and logarithmic) view the plane to be shown can be set to x-y, x-z or y-z plane.
  • if "show radius vector" is selected, the vector from the origin to the planet is drawn
  • "run forwards" selects the direction of time forwards; "run backwards" backwards.
  • "run step wise":if selected and after the Draw Panel was left mouse-clicked, the planets move one step.
    If the left mouse was pressed in the Draw Panel, the planets are moving continously till the left mouse is released.
  • "run continuously": if selected the planets are moving continuously till option "run step wise" is selected or the menu item "stop" of the context menu in planets panel is clicked.
    (s. Draw Panel)

Menu Orbital Parameters

Selecting this menu will show the orbital parameters of the planet, selected in a combo box. In a first table static and dynamic, but non-editable parameters are displayed. In a second table static, editable parameters are shown.

By clicking a parameter in the second table it can be modified. Editing must be terminated by the Enter-key or by clicking another parameter. The modifications will be effective by clicking the apply-button.

The following parameters can be edited:

  • numerical excentricity: valid values [0, 0.9]
  • inclination of the orbital plane vs. ecliptic: valid values [-180, 180]
  • argument of perihelion : valid values [-180, 180]
  • longitude of ascending node vs. x-axis of the ecliptic: valid values [-180, 180]
If a non-valid value was entered, a beep sounds and the focus stays on the last edited cell.

Menu Rise&Transit&Set

Clicking this menu opens a panel, by which the times of rise, upper transit and set of a selectable planet are determined as seen from a location on the observing planet.

Elements of the panel:

  • observer: name of the observing planet
  • location of the observer: geographical longitude and latitude, number of time zone and time zone offset in [days] hours[: minutes]
  • a button to browse for named locations
  • planet, for which rise, transit and set times are to be determined.
  • Date&Time: date&times will be given as GMT date&time or local date&time
  • Start date: the date (as GMT or local date), from which on the first transit is looked for.
  • No of transits: the number of consecutive transits to be determined
  • define rise/set altitude: the altitude of the planet's centre relative to the horizon, which defines rise or set.
    • 0°: center at the horizon
    • -0.56°: center below the horizon due to atmospheric light refraction on the earth as observing planet
    • -6°: center below the horizon, civilian twilight
    • -12°: center below the horizon, nautical twilight
    • -18°: center below the horizon, astronomical twilight
  • text area of the resulting records. Each record consists of the date&times of rise, upper transit and set of the planet. The azimuth is added to rise and set time, the altitude to the transit time.
Rise and set occur, when the centre of the planet reaches the altitude of the rise/set defining altitude relatively to the horizon of the observer's location. This definition is applied for all objects of the solar system including the sun. Another definition of the sun's rise and set does not consider the centre of the sun, but the upper limb of the sun disk, reaching or leaving the horizon. Using this definition results in rise/set times being approximately 2 minutes earlier/later compared with the centre-based times. Applying the twilight definition is meaningful only for the sun observed by a planet with an atmosphere. The refraction angle of the earth is -0.56 degrees. Refraction angles of other planets are not known.

Control Panel

The control panel consists of the following elements:
  • step size: the size of the time steps, the planets are moving in earth days. Editing must be terminated by the Ok-Button.
  • elapsed msecs: the elapsed time in milliseconds for 365 steps in continuous mode
  • a slider, which changes the speed of the moving planets. (to left: slower, to right: faster)
  • date and GMT-time
  • in horizontal view the local date and time at the observing location for the time zone of its  location. The given time zone TZ of a location is its number between -12 and + 12. The time offset to GMT time is TZ * (duration of a sun day in hours)/24.

Draw Panel

This panel shows the positions of the planets in different views. Clicking this panel with the right mouse opens a context menu with:
  • clear screen: clear the screen and show the actual position
  • start planets: start the planets, if the run mode was set to continuous
  • stop planets: stops the movement of the planets
Clicking the left mouse starts the movement of the planets, in run mode 'step wise' as long as the mouse is released.

Orbital Elements

The orbital elements (also known as osculating elements )define the orbital plane of a planet relative to the ecliptic.

The elements of the picture below:

  • vernal equinox of a planet:
    The point at which the planet intersects its equatorial plane in ascending direction.
    The vernal equinox of the earth is the x-axis of the ecliptic.
    Rotating the line of planet's vernal equinox by the negative obliquity results in the planet's rotation axis.
  • a: big half axis of the planet's ellipse
  • e: numerical excentricity:
    distance of the sun from the center of the ellipse= a*e
  • line of nodes of a planet:
    intersection of the orbital plane with the ecliptic
  • Ώ: longitude of ascending node
  • ω: argument of perihelion
  • ωve: argument of planet's vernal equinox
  • ν:  true anomaly
  • E: excentric anomaly:
    the position of a planet on a ellipse is defined by the corresponding position on a circle with radius equal to the big semi axis of the ellipse. The projection of the vector of this position on the semi axis of the ellipse equals the projection of the radius vector of the position on the ellipse.
    The angle of this vector and the big semi axis at the center of the ellipse is the excentric anomaly.
orbital elements

Glossary of Terms

  • Altitude:
    the angle of an object above the horizontal plane of an observer
  • Ascending node:
    position, where a planet crosses the ecliptic in ascending direction (north)
  • Astronomical unit AU:
    mean distance earth-sun, 149,598 Mio km
  • Azimuth:
    the angle of an object on the observer’s horizontal plane, measured vs. south (east: negative; west: positive)
  • Declination:
    the angle of an object above the equatorial plane of the observing planet
  • Descending node:
    position, where a planet crosses the ecliptic in descending direction (south)
  • Ecliptic:
    the reference plane of the planet system. The x-axis is given by the line sun to the earth, when the earth is at the position of its ascending vernal eqinox).
  • Equatorial plane:
    the plane parallel to the equator of a planet
  • VernalEquinox:
    The point at which a planet intersects its equatorial plane in ascending direction.
    The line to this position is the x-axis of planet's equatorial system.
  • GMT date&Time:
    the date and time of the Greenwich meridian, given in date&time of the earth.
  • Greenwich meridian:
    the meridian with geographical longitude 0°.
    As conventon for other planets than earth this meridian is defined as that one, for which the sun passes its lowest altitude at 2001-Jan-1, 0:0hr.
    For the sun as observer the 0-meridian is defined as that one with Greenwich mean sidereal time GMST=0 at 2001-Jan-1, 0:0hr.
  • Greenwich Mean Sidereal Time (GMST):
    • the angle of the Greenwich meridian vs. the planet's vernal equinox in degrees.
      When the sun passes its position with the lowest altitude (anti-cumulation), then GMST=Right Ascension of the planet in planet's fixed heliocentric equatorial system.
  • Horizontal plane:
    tangential plane at the observation point on a planet given by geographical longitude and latitude
  • Latitude:
    angular position on a planet measured vs. equator (north: positive, south: negative)
  • Local date&time:
    the date&time of the local time zone=GMT date&time + time zone * (duration of the planets sun day)/24
  • Local Mean Sidereal Time (LMST) of a location on a planet with a given longitude:
    the angle of the meridian with the given longitude vs. the planet's vernal equinox. LMST=GMST + longitude
  • Location of an observer:
    given by longitude and latitude of the position on the observing planet.
    If a location on an observing planet other than the earth is identified by the name of a city, this location has the same longitude and latitude as this city on the earth.
  • Longitude:
    angular position on a planet vs. Greenwich Meridian (east: positive, west: negative)
  • Obliquity:
    inclination of the orbital plane vs. planet's equatorial plane.
  • Orbit:
    movement of the planet in it's plane
  • Orbital (Keplerian) elements of a planet:
    (s. Orbital Elements):
    • Major axis:
      big semi axis of the ellipse in astronomical units (AU)
    • Numerical excentricity:
      e= (distance of the sun from the centre)/major axis
    • Inclination:
      inclination of the orbital plane versus ecliptic
    • Longitude of ascending node:
      angle between vernal equinox of aries and the position of the planet crossing the ecliptic from south to north
    • Argument of perihelion:
      angle on the planet’s orbit between the ascending node and the perihelion
  • Orbital period:
    time to rotate once around the sun
  • Perihelion:
    the position of the planet with minimum distance to the sun
  • Right ascension:
    angle of the position of an object vs. the vernal equinox in the fixed equatorial system of an observing planet.
  • Rise of a planet:
    coming from below horizon the centre of the planet reaches the rise defining altitude relatively to the horizontal plane of an observer on the observing planet. This is valid for the sun also.
  • Rise/Set defining altitude:
    The center of the planet is below the horizon
    0°, -0.56° (due to atmospheric light refraction of the earth), -6 °(civilian twilight), -12° (nautical twilight) or -18° (astronomical twilight). The only objects of the solar system, which produce twilight, are the sun and the moon.
  • Set of a planet:
    coming from above horizon the center of the planet reaches the set defining altitude relatively to the horizontal plane of an observer on the observing planet. This is valid for the sun also.
  • Sidereal day:
    time to rotate 360 degrees around the axis of rotation (earth: 0.9972 *24 h)
  • Sun day:
    time to rotate once to the same position of the sun (earth: 24 h)
  • Time zone of a location on the observing planet:
    there are 24 time zones. The Greenwich meridian has time zone 0, east of Greenwich meridian time zone >0, west of Greenwich time zone <0. The difference of time offsets of of two adjacent time zones amounts to duration of the planets sun day/24.
  • vernal equinox:
    The point at which the planet intersects its equatorial plane in ascending direction.

Change Log

Version V2.0

  • Most browsers do not support Java Plugin and Java Web Start anymore. So running BoPlanets as an applet is removed.

Version V1.5

  • Unified user interface
  • Because most browsers do not support Java Plugin anymore, the applet of BoPlanets is now started by Java Web Start. The web address of the server, which hosts the applet, must be added to the exception site list of the Java Console, tab Security.
  • Open Help file:
    If BoPlanets runs as a local Java application the help file is opened in the local browser.
    If BoPlanets runs as a Java applet, opening in a local browser is not supported by most browsers. The help file is opened within a Java component with some restrictions e.g. external links could not be opened.
  • Bugfixes

Version V1.3-Up2

  • Input of decimal numbers:
    In menu Observer Locations, when horizontal view was selected, and in menu Rise,Transit&Set-Times the decimal numbers of latitude and longitude were formatted with the Java decimal separator ".". Now decimal numbers are formatted according to the current default locale. For Windows the default locale can be set in System Control-> Regional and Language settings.
  • Results of rise, transit and set times:
    The results can now be viewed completely without horizontal scrolling.
  • Rise, transit and set times of a planet observed by the sun:
    The results were incomplete and it took a pretty long time to produce the results.This bug was corrected.

Version V1.3-Up1

  • The calculation of minimum and maximum altitude for the horizontal view was corrected. If the absolte values of minimum and maximum declination are different, then minimum and maximum altitude for HorizontalView were determined incorrectly. For the natural orbital parameters of the planets this difference is quite small; so the effect of incorrect minimum and maximum altitude is hardly to see. But if orbital parameters are modified, then the difference may be quite significant.

Version V1.3

The main changes regard the presentation of the equatorial and horizontal view. The orbitals of the planets are displayed in all views in such a way, that their maximum and minimum are nearby the margins of the window without distortion. To do that, maximum and minimum of the ordinate and abscissa must be determined. This was done mathematically exact for the ecliptic and logarithmic ecliptic view.

For the equatorial view minimum and maximum declination were approximated. This worked fine, if planet and observing planet were not too near. For adjacent planets as for Mercury/Venus, Venus/Earth, Neptune/Uranus or Neptune/Pluto this method failed; the orbitals did not fit within the actual window size.

BoPlanets lets you modify some of the orbital parameters (s. menu OrbitalParameters). For all combinations of observer and planet there is a parameter combination, for which this approximation failed completely especially for great numerical excentricities.

The maximum and minimum declination was determined in a mathematical exact way by using numerical methods. Now all combinations of observer and planet with their standard orbital parameters are displayed correctly. This is true for most combination of orbital parameters.

The numerical methods used are:
  • method of steepest descent/ascent (gradient method)
  • 2-dimensional Newton method for solving an equation system of two equations.

Downloads

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License

BoPlanets: Copyright (c) Bernd Ostermann 2007;
eMail: ostermann.bernd@arcor.de

The software is provided "as it is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.