Getting NVSS data products by anonymous FTP
The large (4 deg X 4 deg) maps and their associated multisource (u,v) data sets are stored as binary files in FITS format. Maps are stored in gzip compressed form, but an uncompressed form may be requested (see below). Each map is named by the J2000 right ascension and declination of its center, and the first letter specifies the polarization plane(s). For example, C2230P84.gz is the map cube with Stokes I, Q, and U planes centered on right ascension = 22h 30m, declination = +84 deg. I0224M32.gz contains only the total-intensity plane centered on right ascension 02h 24m, declination -32 deg. The corresponding multisource (u,v) data file is called J0224-32.MS. The compressed map cubes are about 1.7 megabytes in size, and the total-intensity maps are smaller (about 0.7 megabytes) for faster access by users not interested in linear polarization. The postscript file paper.ps (about 4.7 megabytes) contains a detailed description of the NVSS. This paper has been published; the reference is Condon, J. J., Cotton, W. D., Greisen, E. W., Yin, Q. F., Perley, R. A., Taylor, G. B., & Broderick, J. J. 1998, AJ, 115, 1693.
A sample anonymous FTP session is shown below:
Compression: The images are stored as standard FITS files compressed in GNU zip (gzip) format, the .gz extension denoting this compression. If an uncompressed version is desired, omit the .gz when requesting the file. Gzipped files may be uncompressed with the command gunzip which is available for most computer systems. See the text file pub/nvss/compress.txt for a more detailed description of gzip.
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