Guide to NED Position Data Search Results

(Latest Revision: 8 May 2009)

This page displays results from searches for position data for an individual object. These position data are distinct from NED's "Basic Data" because they are not only referenced, but accompanied by detailed qualifiers. Within NED, each measurement (single data point) along with its descriptors is called a "Position Data Frame" or a "Position Data Point".

The positions displayed in the Basic Data page are often NOT included in this Position Data page, though each Basic Data position is included in the summary list as No. "0" with its errors and reference.

The position data returned by your search will be presented as an HTML table (default), HTML preformatted text, ASCII text (tab-separated or bar-separated), or in XML (VOTable) format. The HTML output is formatted for easy reading by eye on your computer screen, while the ASCII and XML output is appropriate for parsing by computer scripts or programs. The ASCII and XML tables are preceded by a header line showing the data contents of each column.


The top of this page displays a summary table of the position data frames. The first line shows NED's adopted position for the object, the uncertainty ellipse, and the reference code. The second and following lines include

  • A sequential data-point number applicable to this list only.
  • The position as published, converted to the coordinate system and equinox you specified on the input page,
  • The frequency or wavelength at which the data apply (in common astronomical jargon, e.g. "V" for the Johnson V band, "IRAS 12 microns" for the IRAS 12 micron band, etc.),
  • The 95% uncertainty ellipse (semi-major axis, semi-minor axis, and position angle).
  • The NED 19-digit reference code. The code is linked to the full title or abstract in NED's bibliographic database.

Positions are ordered by increasing semi-major axis of the uncertainty ellipse.

Detailed information for each measurement in the list may be seen by clicking on the sequential number for that measurement, or by scrolling down the page to the measurement.

Detailed data included for each measurement in NED's Position Data Frames are:

  • NED Standard Format:
    • Coordinates in your chosen system and equinox.
    • RA/DEC J2000: The published position transformed into J2000.0 equatorial coordinates, displayed in standard sexagesimal notation. (If you chose J2000.0, this line displays B1950.0 coordinates.)
    • 95% Conf(idence) Ellipse: Semi-major and semi-minor axes, and position angle, of the 95% confidence ellipse for the J2000.0 equatorial coordinates.
    • NED Comment: Notes about any changes made to the data by NED.
  • Measurement as published:
    • Published Name: The name, in NED's standard format, of the object to which the data apply.
    • Coord1/Coord2: The coordinates as published.
    • Unc(ertainty)1/Unc(ertainty)2/Unc(ertainty)PA: uncertainty ellipse, as published, usually standard deviations in RA and Dec; and position angle for the uncertainty ellipse if published.
    • Unc(ertainty) Significance: The type of uncertainty reported in the original publication; e.g. "rms uncertainty", "90% confidence", "no unc. reported", etc.
    • Equinox: The equinox to which the coordinates are referred (usually B1950.0 or J2000.0).
    • Epoch: The date of the observation (if given in the original publication).
    • Freq(uency) or Wave(length): The frequency or wavelength of observation as given in the original publication, or the standard value assumed by NED if not given; the units (if applicable); the frame in which the frequency or wavelength is defined (OBS for observatory reference frame, and REST for object or source rest frame); and the frequency in Hz, as translated by NED.
    • (Coordinate) Sys(tem): Equatorial, Galactic, supergalactic, etc.
    • (Coordinate) Units: Sexagesimal, Decimal Degrees, etc.
    • (Fundamental Reference) Frame: FK3, FK4, FK5, ICR[F], etc.
    • Frequency Mode: The method(s) by which the data were collected, reduced, or derived, in relation to the frequency or wavelength; e.g. "broad-band measurement", "radio-frequency line maps", etc.
    • Qualifiers: Self-explanatory notes pertaining to
      • the history of the data (e.g. "from new raw data", "transformed from previously published data", etc.),
      • adjustments to the data (e.g. "zero-point corrected", etc.)
      • changes introduced by NED (e.g. "obvious typo corrected", "correction published in errata", etc.),
      • values modified by NED (e.g. "Coord1 modified from published value", "Frequency modified from published value", etc.), and
      • assumptions made by NED about the precise parameters of the data (e.g. "FK4 assumed," etc.).
    • Reference code: The literature source for the present photometric data point.
    • Comments: Other information about the data.
  • Reference Point for Relative Positions (suppressed if absolute positions are published).
    • Name: NED formatted name for the reference object or position.
    • (Coordinate) System: Equatorial, Galactic, supergalactic, etc.
    • (Coordinate) Units: Sexagesimal, Decimal Degrees, etc.
    • Coord1/Coord2: The reference coordinates, if published.
    • Uncertainty: as published, usually standard deviation in RA and Dec; and position angle for the uncertainty ellipse if published.
    • Significance: The type of uncertainty reported in the original publication; e.g. "rms uncertainty", "90% confidence", "no unc. reported", etc.

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