NED Tools

This page includes information for NED Tools and other miscellaneous NED services:

• Coordinate Calculator
• Extinction Calculator
• Velocity Calculator
• Position/Offset Plotter

There is also a NED FAQ with answers to frequently asked questions about NED.

Coordinate Precession and Transformation, and Galactic Extinction

This is an easy-to-use coordinate transformation, precession, and position angle calculator provided for your convenience. It is flexible enough to convert accurately between Besselian and Julian equinoxes, taking the epoch of observation into account when needed. It assumes that Besselian dates refer to the FK4 system, that Julian dates refer to the FK5 system, and makes the appropriate transformations. Though the recently-adopted International Celestial Reference Frame (ICRF) is not explicitly supported, the FK5 optical system is consistent with ICRF to within the known errors of the FK5 system (see e.g. Ma et al. AJ 116, 516, 1998).

The coordinate calculator also returns the foreground Galactic extinction (from the maps by Schlegel et al. in ApJ 500, 525, 1998) at your input position. Click here for more information and cautions on using the extinction values returned by the calculator.

Velocity (Redshift) Conversion

Most redshifts for extragalactic objects are published as "heliocentric" velocities -- that is, the earth's rotational and orbital motions have been removed from the object's measured velocity. It is often necessary to further "correct" the redshifts for other motions: Galactic rotation, peculiar motion of the Galaxy within the Local Group, and motion within the reference frame defined by the 3K microwave background radiation. This calculator enables you to make these corrections as needed. NED has several pre-defined apex vectors that you may use, or you may input your own apex vector.

X/Y Offset to RA/Dec

This is a tool to convert rectangular offsets to RA and Dec, given a "central" coordinate (for e.g. a cD galaxy in a cluster) to which the offsets are referred. It assumes a flat field with a fixed plate scale. Field rotation is also accommodated, as is sign reversal (e.g. offset increasing to the south).