Neptune Moon Tracker Help
This form enables you to generate a Postscript file showing the
east-west motion of Neptune's satellites within a specified time period.
The distance of each selected moon from the planet's axis is plotted in
units of either arcsec or Neptune radii. Positive values correspond
to bodies on the "morning" (east) side of Neptune and negative values by
the "evening" (west) side. In the diagram, the limbs of Neptune are
indicated by a dark gray stripe down the middle. The location of the
Adams Ring can be added as a band in lighter gray. Time increases
downward on the plot.
The Moon Tracker tool also allows you to download an ASCII table
containing the numeric values that went into the diagram. The file
contains a single header line followed by the numbers. Columns are as
Modified Julian Date (UTC)
Projected equatorial radius of planet (arcsec)
Distance of first moon from planet's axis (arcsec)
Distance of second moon from planet's axis (arcsec)
1.0 (February 3, 1997):
Original Neptune Moon Tracker on line.
2.0 (January 12, 1999):
Revised user interface.
Extended ephemeris time limits.
2.1 (February 1, 1999):
Added new ephemeris option.
2.2 (December 1, 2009):
Updated the default ephemerides. To reduce confusion, we have removed
the choice about what ephemeris to use.
2.5 (January 23, 2013):
Renumbered for consistency across all the Moon Tracker tools.
2.6 beta (January 4, 2016):
Ported to new server.
The start and stop times (UTC) of the plot can be entered in a variety
of formats. For example, the following all parse to 0:01:02 UTC on July
If you want the gory details of how times are interpreted, click
- 1976-JUL-04 00:01:02.00
- July 4, 1976 12:01:02 am
- 12:01:02 am July 4, 1976
- 1976-07-04T00:01:02Z (PDS format)
- MJD 42963.00071759259
- JD 2442963.50071759259
Enter the time interval to be used for the tabulation as a number in the box,
and select the time unit from the choices provided. Start times and intervals
are rounded to the nearest minute.
Enter the numeric range and units of the horizontal axis. The value
you enter is actually half the width of the diagram; for example, if you
enter 10 Neptune radii, then the axis will run from -10 to 10. Zero
always falls at the middle of the plot.
Enter a title for the plot in this box. It will appear centered above
Click on the box to the left of each moon that you wish to include in the
diagram and in the tabulation.
Click on the box to include the outer boundary of the ring system (i.e.
the Adams Ring) in the plot. It will appear as a
vertical gray stripe on each side of the planet.
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Last updated 4 January 2016.