Registered FITS Conventions

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Registered FITS Convention

The CONTINUE Long String Keyword Convention
Description: The CONTINUE long string keyword convention may be used to assign a character string value to a FITS keyword that is longer than the 68-character limit for the value of a single FITS keyword. Under this convention, the long string value is divided into multiple substrings, each of which is no longer than 67 characters in length. An ampersand character (`&') is appended to every substring, except for the last one. Each substring, enclosed in single quote characters, is written in order to the FITS header. The first substring is given as the value of the specified keyword; the remaining substrings are all written to keywords that have the name CONTINUE in bytes 1 through 8, and have space characters in bytes 9 and 10. Since the CONTINUE keywords do not have the `=' value indicator in byte 9, they have no formal value. FITS readers that do not support this convention should interpret the CONTINUE keywords as being equivalent to a COMMENT keyword.
The following is an example of this convention,
SVALUE  = 'This is a long string value &' 
CONTINUE  'extending&   '   
CONTINUE  ' over 3 lines.'   
that is equivalent to the following single keyword:
SVALUE  = 'This is a long string value extending over 3 lines.'
See the full documentation (available below) for the complete set of rules and recommendations regarding the use of this convention.
See also the extensive discussion of earlier versions of this convention on the FITSBITS email list in May 1993 and July/August 1994.
Submitted: 11-July-2007 by W. Pence, NASA/GSFC (on behalf of the HEASARC)
Registered: October 2007
Date and Place of First Usage: circa 1994, HEASARC
Extent of Usage: Extensively used in data files from the Rossi Timing Explorer (RXTE) mission, and occasionally in data files from other high energy astrophysics missions supported by the HEASARC. It has also been used in some the Chandra data files produced by Chandra X-ray data center. This convention is supported by the CFITSIO library for reading and writing FITS files.
Full Documentation: PDF format, Postscript format
Comments and/or critiques: FITSBITS discussion
Sample FITS File: rxte.fits (from the RXTE mission). In particular, note the descriptive keywords for column 12 of the first table extension in this file.
Sample Header Listing: rxte.txt
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Last revised: Thursday, 18-Oct-2007 15:25:28 EDT
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