WCS failure: CRVAL is truncated significantly

[keflavich]

probably related to #4555

wcs.to_header is dramatically truncating the celestial CRVAL in this header:

SIMPLE  =                    T /Standard FITS
BITPIX  =                  -32 /Floating point (32 bit)
NAXIS   =                    3
NAXIS1  =                  256
NAXIS2  =                  256
NAXIS3  =                  150
EXTEND  =                    T
BSCALE  =   1.000000000000E+00 /PHYSICAL = PIXEL*BSCALE + BZERO
BZERO   =   0.000000000000E+00
BTYPE   = 'Intensity'
COMMENT   1 blank line
BUNIT   = 'JY/BEAM '           /Brightness (pixel) unit
EQUINOX =   2.000000000000E+03
RADESYS = 'FK5     '
LONPOLE =   1.800000000000E+02
LATPOLE =  -5.186266666667E+01
PC01_01 =   1.000000000000E+00
PC02_01 =   0.000000000000E+00
PC03_01 =   0.000000000000E+00
PC01_02 =   0.000000000000E+00
PC02_02 =   1.000000000000E+00
PC03_02 =   0.000000000000E+00
PC01_03 =   0.000000000000E+00
PC02_03 =   0.000000000000E+00
PC03_03 =   1.000000000000E+00
CTYPE1  = 'RA---SIN'
CRVAL1  =   2.409303333333E+02
CDELT1  =  -2.222222222222E-05
CRPIX1  =   1.290000000000E+02
CUNIT1  = 'deg     '
CTYPE2  = 'DEC--SIN'
CRVAL2  =  -5.186266666667E+01
CDELT2  =   2.222222222222E-05
CRPIX2  =   1.290000000000E+02
CUNIT2  = 'deg     '
CTYPE3  = 'FREQ    '
CRVAL3  =   2.563000222540E+11
CDELT3  =   8.549244424438E+05
CRPIX3  =   1.000000000000E+00
CUNIT3  = 'Hz      '
PV2_1   =   0.000000000000E+00
PV2_2   =   0.000000000000E+00
RESTFRQ =   2.562999000000E+11 /Rest Frequency (Hz)
SPECSYS = 'LSRK    '           /Spectral reference frame
ALTRVAL =  -1.429997716196E+02 /Alternate frequency reference value
ALTRPIX =   1.000000000000E+00 /Alternate frequency reference pixel
VELREF  =                  257 /1 LSR, 2 HEL, 3 OBS, +256 Radio
COMMENT casacore non-standard usage: 4 LSD, 5 GEO, 6 SOU, 7 GAL
TELESCOP= 'ALMA    '
DATE-OBS= '2015-01-03T14:21:52.416000'
TIMESYS = 'UTC     '
OBSRA   =   2.409303333333E+02
OBSDEC  =  -5.186266666667E+01
OBSGEO-X=   2.225142180269E+06
OBSGEO-Y=  -5.440307370349E+06
OBSGEO-Z=  -2.481029851874E+06
DATE    = '2015-11-11T16:43:54.590000' /Date FITS file was written
ORIGIN  = 'CASA 4.2.2 (prerelease r30986)'
CASAMBM =                    T /CASA multiple BEAMS table present
END

w = wcs.WCS(fits.Header.fromtextfile('test.hdr'))
w.to_header()

yields:

WCSAXES =                    3 / Number of coordinate axes
CRPIX1  =                129.0 / Pixel coordinate of reference point
CRPIX2  =                129.0 / Pixel coordinate of reference point
CRPIX3  =                  1.0 / Pixel coordinate of reference point
CDELT1  =  -2.222222222222E-05 / [deg] Coordinate increment at reference point
CDELT2  =   2.222222222222E-05 / [deg] Coordinate increment at reference point
CDELT3  =   8.549244424438E+05 / [Hz] Coordinate increment at reference point
CUNIT1  = 'deg'                / Units of coordinate increment and value
CUNIT2  = 'deg'                / Units of coordinate increment and value
CUNIT3  = 'Hz'                 / Units of coordinate increment and value
CTYPE1  = 'RA---SIN'           / Right ascension, orthographic/synthesis project
CTYPE2  = 'DEC--SIN'           / Declination, orthographic/synthesis projection
CTYPE3  = 'FREQ'               / Frequency (linear)
CRVAL1  =                240.9 / [deg] Coordinate value at reference point
CRVAL2  =                -51.9 / [deg] Coordinate value at reference point
CRVAL3  =       256300022254.0 / [Hz] Coordinate value at reference point
PV2_1   =                  0.0 / SIN projection parameter
PV2_2   =                  0.0 / SIN projection parameter
LONPOLE =                180.0 / [deg] Native longitude of celestial pole
LATPOLE =       -51.8626666667 / [deg] Native latitude of celestial pole
RESTFRQ =       256299900000.0 / [Hz] Line rest frequency
RADESYS = 'FK5'                / Equatorial coordinate system
EQUINOX =               2000.0 / [yr] Equinox of equatorial coordinates
SPECSYS = 'LSRK'               / Reference frame of spectral coordinates
OBSGEO-X=        2225142.18027 / [m] ITRF observatory X-coordinate
OBSGEO-Y=       -5440307.37035 / [m] ITRF observatory Y-coordinate
OBSGEO-Z=       -2481029.85187 / [m] ITRF observatory Z-coordinate
MJD-OBS =        57025.5985233 / [d] MJD of observation matching DATE-OBS
DATE-OBS= '2015-01-03T14:21:52.416000' / ISO-8601 observation date matching MJD-

Look at CRVAL:
CRVAL1 = 2.409303333333E+02 to

CRVAL1 = 240.9

In [26]: w.to_header()['CRVAL1'] - w.wcs.crval[0]
Out[26]: -0.030333333300006871

Issue was originally identified from radio-astro-tools/spectral-cube#280

[keflavich]

...sorry, this appears to be fixed on master, I hadn't pulled the latest.

[keflavich]

I would guess this PR fixed it

[astrofrog]

By the way, this is an issue in Astropy 1.1.x but not 1.0.x