Neptune Ephemeris Generator Help

This form enables you to generate a table listing useful information about the viewing geometry for Neptune and/or any of its moons as a function of time. You are free to specify which of a variety of useful quantities to tabulate. The file returned will contain a single header line describing each column, followed by one row of numbers for each time step.

Change History

1.0 (February 3, 1997): Original Neptune Ephemeris Generator on line.
1.1 (February 6, 1997): Added optional columns for sub-solar and sub-Earth inertial longitudes.
2.0 (January 12, 1999): Added sub-solar and sub-Earth latitude/rotating longitude options. Revised user interface. Extended ephemeris time limits.
2.1 (February 1, 1999): Added a new ephemeris option.
2.2 (January 10, 2003): Added a new column option providing second accuracy in time tags.
2.3 (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): Raised the maximum number of output lines to 10,000. Renumbered for consistency across all the Ephemeris Generator tools. Ephemeris updates.
2.5.1 (February 28, 2014): Added S/2004 N 1.
2.6 (January 4, 2016): Ported to new server. Ephemeris updates.
2.7 (October 14, 2020): Ephemeris updates, updated name of "Hippocamp".
2.8 (June 20, 2021): Ephemeris updates.
3.0 (August 2, 2022): Major new features:
- the selection of available columns has been expanded and standardized across all Ephemeris Generator tools.
- Ephemeris Generator requests can now be bookmarked.
- the new Output option lets you jump directly to the table, bypassing the web page.
- JWST, HST, and Earth-based observatories are now supported.
- the form now uses a clean, new style sheet.

Time Limits

The start and stop times (UTC) of the table 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 (ISO 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.

Viewpoint

You may specify the point of view of the diagram. By default, the point of view is the center of the Earth.

Observatory: You may select from any viewpoint on the list.

Earth's center
JWST: Valid for 2021-Dec-25 to approximately two years after the present day.
HST: Valid for 1990-Apr-25 to approximately two months after the present day.
Named observatories: After each observatory's name, you will see listed its latitude and east longitude in degrees, followed by its altitude in meters. Note that only very rarely will a diagram change significantly based on the particular location of an Earth-based observatory.

Latitude & Longitude: If your desired observatory or location is not on the observatory list, you can enter its latitude, longitude and altitude in the three boxes provided. Latitudes and longitudes can each be specified by up to three values, interpreted as degrees, minutes and seconds. Longitudes can be specified either east or west.

If you wish to have an observatory added to the standard list, or to refine the coordinates of a listed observatory, email the necessary information to pds-admin@seti.org.

General Column Selection

Click on the box to the left of each quantity or set of quantities that you wish to tabulate. The order of the columns in the table will match the order listed on the form. Possible selections are as follows:

Modified Julian Date
Adds a column containing the Modified Julian Date, a common method of designating dates and times in astronomy. MJD is equal to the number of (possibly fractional) days elapsed since 0:00 UTC on 17 November 1858.
Year, Month, Day, Hour, Minute
Adds five columns containing the UTC date (year, month, day) and time (hours, minutes) as integers.
Year, Month, Day, Hour, Minute, Second
Adds six columns containing the UTC date (year, month, day) and time (hours, minutes, seconds) as integers.
Year, DOY, Hour, Minute
Adds four columns containing the UTC date (year and day-of-year) and time (hours, minutes) as integers.
Year, DOY, Hour, Minute, Second
Adds five columns containing the UTC date (year and day-of-year) and time (hours, minutes, seconds) as integers.
Observer-Neptune distance
Adds a column containing the distance between the observer and Neptune, in km.
Sun-Neptune distance
Adds a column containing the distance between the Sun and Neptune, in km.
Neptune phase angle
Adds a column containing the phase angle of Neptune as seen from the observer, in degrees. This is equal to the Sun-Neptune-observer angle.
Ring opening angle to the observer
Adds a column containing the ring plane opening angle to the observer, in degrees. This is equivalent to the planetocentric sub-observer latitude at Neptune; it equals zero during a ring plane crossing.
Ring opening angle to the Sun
Adds a column containing the ring plane opening angle to the Sun, in degrees. This is equivalent to the planetocentric sub-solar latitude at Neptune; it equals zero during a ring plane crossing.
Sub-observer inertial longitude
Adds a column containing the sub-observer longitude at Neptune, in degrees. This is measured from the J2000 ascending node of the planet's equatorial plane. Note that it is an inertial longitude, not measured in a frame rotating with the planet.
Sub-solar inertial longitude
Adds a column containing the sub-solar longitude at Neptune, in degrees. This is measured from the J2000 ascending node of the planet's equatorial plane. Note that it is an inertial longitude, not measured in a frame rotating with the planet.
Sub-observer latitude and rotating longitude
Adds a pair of columns containing the sub-observer planetocentric latitude and longitude at Neptune, in degrees. This is measured in a frame rotating with the planet.
Sub-solar latitude and rotating longitude
Adds a pair of columns containing the sub-dolst planetocentric latitude and longitude at Neptune, in degrees. This is measured in a frame rotating with the planet.
Neptune RA and Dec
Adds two columns containing the J2000 right ascension and declination of Neptune. RA is tabulated in units of hours; declination is in units of degrees.
Neptune projected equatorial radius
Adds a column containing the projected equatorial radius of Neptune as seen from the observer, in arcseconds.
Lunar phase angle
Adds a column containing the phase angle of the Moon at the specified time, in degrees. A value near zero corresponds to a full moon; a value near 180 corresponds to a new moon.
Sun-Neptune sky separation angle
Adds a column containing the angular separation on the sky from Neptune to the Sun, in degrees. A Sun-Neptune value near zero corresponds to solar conjunction; a value near 180 corresponds to opposition.
Moon-Neptune sky separation angle
Adds a column containing the angular separation on the sky from Neptune to the Moon, in degrees.

Moon Column Selection

You may also include the positions of any set of moons in the table. Any of these quantities can be tabulated for each moon:

Sub-observer latitude and rotating longitude
Adds a pair of columns containing the sub-observer planetocentric latitude and longitude at the selected moon, in degrees. This is measured in a frame rotating with the moon.
Sub-solar latitude and rotating longitude
Adds a pair of columns containing the sub-dolst planetocentric latitude and longitude at the selected moon, in degrees. This is measured in a frame rotating with the moon.
RA and dec
Adds a pair of columns containing the J2000 right ascension and declination for each selected moon. RA values are given in units of hours; dec values are given in degrees.
Offset RA and dec
Adds a pair of columns containing the positional offset of each selected moon from the center of the planet. Values are given in units of arcseconds, where the first value is the offset in the direction of increasing J2000 RA and the second is in the direction of increasing dec.
Orbital longitude relative to observer
Adds a column containing the orbital longitude of the selected moon relative to the observer, in degrees. Zero indicates that the moon is between the observer and the planet; 90 indicates that the moon is at the receding ansa.
Orbit plane opening angle to observer
Adds a column containing the opening angle of the orbit plane as seen from the observer, in degrees.

Moon Selection

Click on the box to the left of each moon that you wish to include in the table. Note that it is not necessary to include any moon columns at all.

Output

By default, when you click on "Generate table", you are directed to a web page that lists the details of the request and a small preview. Optionally, you can choose to bypass the web page and go directly to table format.