[fitsbits] Start of the CONTINUE keyword Public Comment Period

[Doug Mink]

William Pence wrote:
> This is to announce the start of the 30-day Public Comment Period on
> the CONTINUE keyword convention that has been submitted for inclusion in
> the 'Registry of FITS Conventions' which is maintained by the IAU FITS
> Working Group. 

As no one has mentioned it yet, I would like to point out that there is a
huge amount of optical data in FITS files which use the IRAF multi-keyword
continuation method.  A 1-4 letter keyword is followed by an underscore and
three-digit sequence number.  The way I deal with them in WCSTools is to look
for the base keyword and if it is not found look for <base>_001.  If that is
found, I look for <base>_002 and so forth, appending each string to the previous
one, until a keyword is not found.  An advantage is that the keywords do not
have to be contiguous or even in the correct order because the order is
documented in the keyword name.

A typical usage is the storage of polynomial projection coefficients for the
IRAF TNX world coordinate system (tangent plane + polynomial correction) as
shown below.  Support for reading this projection is included in WCSTools.

-Doug Mink

  . . .
WAT0_001= 'system=image'
WAT1_001= 'wtype=tnx axtype=ra lngcor = "3. 4. 4. 2. -0.05837385199330483 0.070'
WAT2_001= 'wtype=tnx axtype=dec latcor = "3. 4. 4. 2. -0.05837385199330483 0.07'
TRIM    = 'Jul 25 21:28 Trim data section is [1:2047,1:4093]'
OVERSCAN= 'Jul 25 21:28 Overscan section is [2054:2100,100:4100] with mean=1064'
CCDSEC  = '[1:2047,1:4093]'
CCDMEANT=            775260912
CCDPROC = 'Jul 25 22:15 CCD processing done'
ZEROCOR = 'Jul 25 22:15 Zero level correction image is z1.fits'
RADECSYS= 'FK5     '
CTYPE1  = 'RA---TNX'
CTYPE2  = 'DEC--TNX'
CRVAL1  =     53.3071726192818
CRVAL2  =    -27.7173865733127
CRPIX1  =     1033.73520722181
CRPIX2  =     1673.69444794591
CD1_1   =  5.61383748782434E-5
CD1_2   =  -1.5386025841724E-7
CD2_1   =  3.38555565395686E-7
CD2_2   =  5.59724101379682E-5
WAT1_002= '44519483406535 -0.09397437792791556 0.1451290667953512 -4.3273459822'
WAT1_003= '97552E-5 4.525801441223172E-4 0.009912907609377613 0.185709640211661'
WAT1_004= '6 1.874028266281251E-5 0.01797451858969125 0.04459426127294047 0.010'
WAT1_005= '87988458562529 -0.1525431073290788 -0.00297118661606969 "'
WAT2_002= '044519483406535 -0.09397437792791556 0.1451290667953512 -4.808546205'
WAT2_003= '327283E-5 4.148865918405720E-4 0.01180811673900729 0.087140524550311'
WAT2_004= '24 -9.417303440113919E-4 0.03105863709218507 0.3049773562603359 0.01'
WAT2_005= '469707839868787 0.0440181026974359 0.1257086385879256 "'
  . . .