Jingo Display
The example above is an
overview of the Solar System including Halley's comet and Sedna.
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Int.
Step= |
The time step (days) used for the numerical
integration. In most examples this is variable and calculated automatically
by the system. |
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Bodyname-Bodyname |
Appears immediately after the Int. Step
information. It shows the two bodies that are determining the
integration step size. For the Solar System this is normally the
Sun and Mercury but can change during other close approaches. |
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Display
Step= |
Shows the integration period between each
screen refresh. Can be increased or decreased by use of the
speed
control except when fixed as a "strobe" (see below). |
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Rel.
Energy= |
Shows the relative energy (potential and
kinetic) in the system. It is calculated as (change in
energy)/(original energy) and is a measure of the accuracy of the
integration. |
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J=nnnn.nnn |
Shows the number of Julian Days since the start of the integration
or actual Julian date if a starting date was supplied. |
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Body names |
The bodies included in the integration are listed on the left in
the colours used to draw them. |
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T=dd/mm/yyyy |
This shows the Gregorian Date of the integration step if a
starting date was supplied. |
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Controls
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Mouse usage |
Left click and drag in the display area to move the whole image.
Right click in the display area to re-centre the original object. |
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Stop |
Click once to stop the
integration. Click again to continue. |
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Speed |
Left click to increase
speed. Right click to reduce speed. (See notes below.) |
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Zoom |
Left click to zoom in and
right click to zoom out. |
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Tilt |
Left click to tilt the
lower part of the display “towards” the viewer. Right click to
tilt the other way. |
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Rotate |
Left click to rotate the
entire view anticlockwise. Right click to rotate clockwise. |
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Clear |
Click to clear the trails. |
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Back |
Click to reverse
direction. |
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Info |
Click to toggle
information on and off, (display of time step, relative energy and
object names). |
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Orbit |
Click to toggle between
displays of object trails or complete orbits. If no central body is defined
then simply toggles between trails and no trails. |
Notes
Using the Speed
control: When you want to "fast forward" to a date, press and hold
the left mouse button over the Speed
control. Watch the Display Step and let
it rise to a few tens of days. As you near the desired date press and
hold the right mouse button until you have reduced the
Display Step and the interval between displays to a suitable
size for viewing the event you are interested in (say 1 day or less).
When "strobe" is in use the Display Step cannot be changed. Maximum
speed will be limited by the power of the machine you are using.
Higher speeds can be achieved when Orbits
are switched off.
Variable
Integration Steps: When variable integration steps are in use you
will see the names of the two bodies used to calculate the step size.
This is done by finding the nearest "close encounter" taking into
account the velocity and distance between objects. In the Solar System
the Sun and Mercury will usually determine the step size but this can
change to some other pair during close encounters.
Orbit Display:
Orbits will only be available using the
Orbit control when there is one major central body (such as the
Sun) in the system. At each display step the
osculating elements of the bodies are calculated and the complete
orbit drawn accordingly. Currently the orbit display will only work
for objects with eccentricity less than 1.0.
Relative
Energy: The total energy in the system is the sum of potential and
kinetic energy. A good Integrator should loose or gain no energy. Most
of these integrations are set up to have an error less than one part
in a billion (1.0E-9). If the error goes much greater than this (say
more than 1.0E-7) the integration may be unreliable.
Accuracy:
The accuracy of most of these simulations is such that a planet (e.g.
Earth) will not be out of position by more than a screen pixel during
a 1000 year integration.
Strobe Effect:
When the strobe effect is in use the Display Step is set equal to the
Period of one of the planets. That planet therefore appears static.
This is useful to highlight certain relationships between orbits. The
apparent positions of other planets may be erratic.
Rotating Coordinates: When rotating coordinates are in use, the
entire system is continuously rotated so that one particular object is
always in the same direction relative to the central object. This is
useful to highlight certain relationships between orbits. The movement
of other objects can appear erratic when this is in effect. |
