Source Positions

There are three different types of positions you can enter: a simple position, a sequence of positions including motion terms and time ranges, and an ephemeris table. The default, in the first tab-page below the source name and aliases, is "simple position". Select a coordinate system (and equinox) in which you specify the coordinates and if you care, also supply distance (if known) and the uncertainties. For anything else than the default ("simple position") use FILE - CREATE NEW - SOURCE POSITION. The dialog box will ask you which type of position you require, and a new selection will redraw the position table accordingly with all variables defaulted. You can upload an ephemeris table (click the link for an example of the ephemeris table format), or you can specify the position and some motion terms valid for some time range. Motion terms are entered as polynomials in time [display]\rm position\ at\ Reference\ Time\ in\ Equinox + value(1) \times time + value(2) \times time^2 + value(3) \times time^3, etc [/display]  Press the [+] for each extra motion term, enter the value and choose the order of the polynomial in time. The motion term units and uncertainty will help recalculating the position (and error) at the time of observations, though this is currently (early 2009) not yet implemented. Leave the motion terms at zero if the source is considered not to move in the specified time interval. If you need another position and/or different motion terms for another time interval, simply add another position to the previous one using the same FILE - CREATE NEW - SOURCE POSITION. Delete old or obsolete positions using the tick-box in the upper left of a position table and EDIT - CUT - CUT SOURCE POSITIONS.

Connect with NRAO

The NSF National Radio Astronomy Observatory and NSF Green Bank Observatory are facilities of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Founded in 1956, the NSF NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NSF NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NSF NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NSF NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.

The U.S. National Science Foundation (U.S. NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."

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