taskGNU Astronomy Utilities - Tasks: task #14625, Option to write a keyword title

 
 

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task #14625: Option to write a keyword title

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Wed 06 Sep 2017 08:50:34 AM UTC
   
 
Should Start On:  Tue 05 Sep 2017 10:00:00 PM UTC Should be Finished on:  Tue 05 Sep 2017 10:00:00 PM UTC
Category:  Fits Priority:  5 - Normal
Item Group:  Enhancement Status:  Postponed
Privacy:  Public Assigned to:  None
Percent Complete:  0% Open/Closed:  Open
Effort:  0.00

Wed 06 Sep 2017 08:50:34 AM UTC, original submission:  

The FITS standard recognizes blank keyword lines and also comment lines (starting with `\'). These features help write the keywords in related groups in an easy to read (by eye) format, for example this output of Gnuastro's Crop program:


XTENSION= 'IMAGE   '           / IMAGE extension
BITPIX  =                  -32 / number of bits per data pixel
NAXIS   =                    2 / number of data axes
NAXIS1  =                  251 / length of data axis 1
NAXIS2  =                  251 / length of data axis 2
PCOUNT  =                    0 / required keyword; must = 0
GCOUNT  =                    1 / required keyword; must = 1
BUNIT   = 'ELECTRONS/S'        / physical units

                      / WCS information
WCSAXES =                    2 / Number of coordinate axes
CRPIX1  =               2003.5 / Pixel coordinate of reference point
CRPIX2  =               -996.5 / Pixel coordinate of reference point
PC1_1   =             -1.0E+00 / Coordinate transformation matrix element
CDELT1  =  1.66666666666670E-05 / [deg] Coordinate increment at reference point
CDELT2  =  1.66666666666667E-05 / [deg] Coordinate increment at reference point
CUNIT1  = 'deg'                / Units of coordinate increment and value
CUNIT2  = 'deg'                / Units of coordinate increment and value
CTYPE1  = 'RA---TAN'           / Right ascension, gnomonic projection
CTYPE2  = 'DEC--TAN'           / Declination, gnomonic projection
CRVAL1  =            53.122751 / [deg] Coordinate value at reference point
CRVAL2  =           -27.805089 / [deg] Coordinate value at reference point
LONPOLE =                180.0 / [deg] Native longitude of celestial pole
LATPOLE =           -27.805089 / [deg] Native latitude of celestial pole
RADESYS = 'FK5'                / Equatorial coordinate system
EQUINOX =               2000.0 / [yr] Equinox of equatorial coordinates

                      / Crop information
ICF1_1  = '/path/to/input/image/in/computer/'
ICF1PIX = '2733:2983,2803:3053' / Range of pixels used for this output.

                      / Versions and date
DATE    = '2017-09-06T08:29:02' / file creation date (YYYY-MM-DDThh:mm:ss UT)
CFITSIO = '3.41    '           / CFITSIO version.
WCSLIB  = '5.16    '           / WCSLIB version.
GSL     = '2.4     '           / GNU Scientific Library version.
GNUASTRO= '0.3.57-ae2f'        / GNU Astronomy Utilities version.
COMMIT  = 'v0-8-g91809f5'      / Git's commit description in running dir.
END


With this task, I am suggesting an option (maybe named) `--keygrouptitle') to allow the users to create such titles and subsequently write related keywords in the FITS HDU together under it.

The focus of FITS keywords is mainly for software reading them automatically and that is indeed the major use case. But when they are nicely categorized in such a fashion, people will be encouraged to look at them directly, with a command like the one below, and get a good general feeling of the dataset's meta-data.


$ astfits -p image.fits


Mohammad Akhlaghi <makhlaghi>
Group administrator

 

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