Neptune Moon Tracker 2.1 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
follows:
Modified Julian Date (UTC)
Year
Month
Day
Hour
Minute
Projected equatorial radius of planet (arcsec)
Distance of first moon from planet's axis (arcsec)
Distance of second moon from planet's axis (arcsec)
etc.
Change History
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.
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
4, 1976:
- 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
If you want the gory details of how times are interpreted, click
here.
Interval:
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.
Currently, the Neptune Ephemeris Generator can use one of two different
ephemerides. Under most circumstances the last option is to be preferred since
it is most recent and therefore most accurate.
-
#1: Best JPL ephemeris as of early 1997. It uses JPL ephemeris NEP016
for the major satellites (Triton and Nereid) and NEP022 for the inner,
smaller satellites. Valid for the period 1979-Dec-29 to 2011-Jan-02
(NEP016) and 1996-Jan-01 to 2004-Dec-31 (NEP022).
-
#2: Same as the above, but using the latest JPL planetary ephemeris DE405
for Neptune, Earth and Sun, beginning 1997-Jan-01.
Scale:
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.
Title:
Enter a title for the plot in this box. It will appear centered above
the diagram.
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.
Neptune Moon Tracker Form |
Rings Node Tools |
Rings Node Home
Last updated 1 February 1999
Mark Showalter