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SECTION 4. HEADERS

When the value of DATE-OBS is expressed in the two-digit year form, allowed for files

written before January 1, 2000 with a year in the range 1900-1999, there is no default

assumption as to whether it refers to the start, middle or end of an observation.

DATExxxx Keywords  The value fields for all keywords beginning with the string DATE

whose value contains date, and optionally time, information shall follow the prescriptions

for the DATE-OBS keyword.

TELESCOP Keyword  The value field shall contain a character string identifying the

telescope used to acquire the data associated with the header.

INSTRUME Keyword  The value field shall contain a character string identifying the

instrument used to acquire the data associated with the header.

OBSERVER Keyword  The value field shall contain a character string identifying who

acquired the data associated with the header.

OBJECT Keyword  The value field shall contain a character string giving a name for

the object observed.

4.4.2.3

Bibliographic Keywords

AUTHOR Keyword  The value field shall contain a character string identifying who

compiled the information in the data associated with the header. This keyword is

appropriate when the data originate in a published paper or are compiled from many

sources.

REFERENC Keyword  The value field shall contain a character string citing a refer-

ence where the data associated with the header are published. It is recommended

that either the 19-digit bibliographic identifier used in the Astrophysics Data System

bibliographic databases (http://adswww.harvard.edu/) or the Digital Object Identifier

(http://doi.org) be included in the value string when available (e.g., '1994A&AS..103..135A'

or 'doi:10.1006/jmbi.1998.2354').

4.4.2.4

Commentary Keywords

These keywords provide commentary information about the contents or history of the

FITS file and may occur any number of times in a header. These keywords shall have

no associated value even if the value indicator characters `= ' appear in bytes 9 and 10

(hence it is recommended that these keywords not contain the value indicator). Bytes 9

FITS Standard