Astronomical Coordinate Conversions


  • For security reasons, your text input is no longer repeated in the form above.
  • The results reported from this conversion are good to approximately 0.5 arcsecond. For a more accurate coordinate conversion application, we suggest:, which is part of the AstroPY Python module.
  • All input coordinates are in DEGREES.
  • The "Coordinate Format" element controls both input and output formats. If "Deg:Min:Sec" is selected, both input coordinates must be in this format.
  • Epochs should be entered as a number: 2000 or 1950. FK5 precession coefficients are used, as specified in the "Astronomical Almanac Explanatory Supplement", 1992, p104, Table 3.211.1.
  • A small error creeps into the calculations when working with epochs earlier than 1550; this error increases as the epoch becomes earlier. At J0000, this error is about 2.2 arcseconds. It can be illustrated by entering RA/DEC of 0,0 and setting both the input and output epochs to zero; in this case, the RA/Dec and Ecliptic Long/Lat should all be zero but are not.

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Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Thomas M. Essinger-Hileman
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