Topocentric Positions of Major Solar System Objects and Bright Stars
Astronomical Applications Dept. Astronomical Applications Dept.
 
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This data service provides topocentric position data for the major solar system bodies and selected bright stars.

Data will be provided for a three year period from 1 January of the preceding year through 31 December of the following year. For dates outside of this range, see MICA and our other data services.

Use Form A for cities or towns in the U.S. or its territories. Use Form B for all other locations. Both forms are immediately below.

Be sure to read the Notes section (on this page beyond the two forms) for definitions and additional details on the data.

Form A - U.S. Cities or Towns

             

      Universal Time (UT1)

  (1 to 9999)

  

  

The place name you enter above must be a city or town in the U.S. The place's location will be retrieved from a file with over 22,000 places listed. Either upper- or lower-case letters or a combination can be used. Spell out place name prefixes, as in "East Orange", "Fort Lauderdale", "Mount Vernon", etc. The only exception is "St.", which is entered as an abbreviation with a period, as in "St. Louis". You need only enter as many characters as will unambiguously identify the place.

  (-90 to 10999)  meters  

If the observer's height above sea level is known, you may enter it here. If unknown, sea level will be assumed.

Form B - Locations Worldwide

             

      Universal Time (UT1)

  (1 to 9999)

 

The place name you enter above is merely a label for the table header; you can enter any identifier, or none (avoid using punctuation characters). The data will be calculated for the longitude and latitude you enter below.

Longitude:          
Latitude:          

  (-90 to 10999)  meters  

If the observer's height above sea level is known, you may enter it here. If unknown, sea level will be assumed.

Need coordinates?  Try NGA's GEOnet Names Server (GNS).
Need U.S. coordinates?  Try the USGS Geographic Names Information System (GNIS).

Notes

Topocentric: With reference to, or pertaining to, a point on the surface of the Earth.

Apparent position: A calculated apparent position corresponds most closely to the observed position of an object on the celestial sphere. The aberration of light (due to the velocity of the observer) and the relativistic bending of light (due to the Sun's gravitational field) are taken into account. For solar system objects, light propagation time is also included.

Right Ascension: Angular distance on the celestial sphere measured eastward along the celestial equator from the equinox to the hour circle passing through the celestial object.

Declination: Angular distance on the celestial sphere north or south of the celestial equator. It is measured along the hour circle passing through the celestial object.

Distance: The distance from the observers position on the surface of the Earth to the Solar System object, given in Astronomical Units (Kilometers for the Moon). Not calculated for stars.

Zenith Distance: Angular distance on the celestial sphere measured along the great circle from the zenith to the celestial object. Zenith distance is 90° minus altitude.

Azimuth: the angular distance measured clockwise along the horizon from a specified reference point (usually north) to the intersection with the great circle drawn from the zenith through a body on the celestial sphere.

True Equator and Equinox of Date: This coordinate system is oriented with its xy-plane parallel to the true instantaneous Earth equator at the time of observation, and its z-axis pointing toward the true instantaneous north celestial pole. The x-axis points toward the true instantaneous equinox. This coordinate system is useful for expressing the positions of observed objects with respect to Earth-based equatorially-mounted instruments.

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