Current Settings

Specify Observer Location:

You can specify a topocentric observer location by choosing from a list of major world cities, by choosing from a list of world-wide observatories, or by giving the latitude, longitude, and altitude. You can also specify non-topocentric Horizons-specific location codes such as the sun or another planet.

Please select from from the following list:

• lookup a named location
• choose from a list of locations
• specify latitude, longitude, and altitude

Use observatory code numbers (if you know them) or names. For example, enter "675" to select the Palomar Mountain main site. Or, enter "palomar" for a list of matching sites. Use "Geocentric or code "500" for geocentric. You can also enter Horizons-specific non-topocentric location codes. For example, use "@sun" to place the observer at the center of the sun, "@0" to select the solar-system barycenter, or "Viking 1@499" to select the Viking 1 landing site on Mars (499). To see all sites available for a specific body, use "*@body" where body is body ID. For example, "*@499" will show all sites on Mars. See the Horizons documentation for more details on center/observer location codes.

Longitude and Latitude can be entered as either "degrees minutes seconds" or decimal degrees. In either case, they should alway be positive and use the appropriate East/West and North/South selections. If entering "degrees minutes seconds" use spaces or commas between elements. If Altitude is unknown, zero can be used for optical sites without much loss of accuracy.