Last updated 1995 October 20 2100 GMT

	This file contains revisions to the NOST Definition
of FITS dealing with the subject of units for angular measure and
celestial coordinates.  They have been approved by a NOST
Accreditation Panel for incorporation in the NOST
Standard, for version 1.1 of the Definition of FITS. 

------------------------------------------------------------------------
	DRAFT REVISIONS TO NOST STANDARD, DEFINITION OF FITS


o  In Section 5.2.2.5, expand the definition of BUNIT to include the
sentence "If the value of BUNIT represents an angular measure, the
use of decimal degrees is recommended." 

o  In Section 5.2.2.5, expand the definition of CRVALn to include the
sentence "If CTYPEn denotes a celestial coordinate, such as right
ascension or declination, CRVALn shall be expressed in units of
decimal degrees." 

o  In the same section, expand the definition of CDELTn to include the
sentence "If CTYPEn denotes a celestial coordinate, such as right
ascension or declination, CDELTn shall be expressed in units of
degrees." 

o  For CROTAn, leave the definition as is -- it already specifies 
degrees.

o  Add a Section 5.4 entitled "Units".  As this is in Section 5, it
pertains to the units of header keywords.  The text would simply read 

"The units of all FITS header keyword values, with the exception of
measurements of angles, should conform with the recommendations in the
IAU Style Manual [7]. For angular measurements degrees are the
recommended units (with the value of BUNIT = 'deg    '), and degrees
are the required units for celestial coordinate systems specified with
the CTYPEn, CRVALn, CDELTn, and CROTAn keywords." 
  
o  In Section 8.1.2, expand the definition of TUNITn to include the
sentence "If the quantity in field n represents an angular measure,
the use of decimal degrees is recommended (TUNITn = 'deg     ')." 

In Appendix C.

o	Item 11a, BUNIT keyword, add "The FITS papers also recommend
the use of degrees as the appropriate unit for angles. This standard 
incorporates that recommendation, specifying decimal degrees."

o	After item 11b, add a new item, "CRVALn, CDELTn, and CROTAn
keywords - This standard extends the recommendations to coordinate
axes, explicitly requiring decimal degrees for celestial coordinates."

  Indexes of remaining items would be adjusted.

o	After item 16 add a new item 

"Section 5.4 Units
The FITS papers recommend the use of SI units and identify certain
other units standard in astronomy.  This standard codifies the
recommendation and makes it more specific by referring to the IAU
Style Manual [7] while explicitly identifying degrees." 

o	Current item 23a, TUNITn keyword, add to the last sentence
"while recommending the use of degrees as the unit for angles."