========================== psfnight-CAMERA-NIGHT.fits ========================== :Summary: PSF model for the night derived from combining multiple arc lamp calibration exposures. :Naming Convention: ``psfnight-CAMERA-NIGHT.fits``, where ``CAMERA`` is *e.g.*, "b0", "r5", etc. and ``NIGHT`` is the observation night in YYYYMMDD format. :Regex: ``psfnight-[brz][0-9]-[0-9]{8}\.fits`` :File Type: FITS, 1 MB Contents ======== ====== ======= ======== =================== Number EXTNAME Type Contents ====== ======= ======== =================== HDU0_ XTRACE IMAGE Legendre coefficient of the fiber trace X CCD coordinates HDU1_ YTRACE IMAGE Legendre coefficient of the fiber trace Y CCD coordinates HDU2_ PSF BINTABLE Table with PSF shape parameters ====== ======= ======== =================== FITS Header Units ================= HDU0 ---- EXTNAME = XTRACE Encodes the X coordinate of the fiber traces in the CCD. X is in units of pixels, along the cross-dispersion axis (perpendicular to the fiber traces) and increases with increasing fiber number. XTRACE is a 2D array of size [nfiber,ncoef]. Each row contains the Legendre polynomial coefficients for a fiber trace. The polynomial applies to a reduced wavelength = (2*wavelength-(WAVEMIN+WAVEMAX))/(WAVEMAX-WAVEMIN) where WAVEMIN and WAVEMAX are header keywords. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ======== ============= ===== ===================== KEY Example Value Type Comment ======== ============= ===== ===================== NAXIS1 7 int length of data axis 1 NAXIS2 500 int length of data axis 2 FIBERMIN 0 int FIBERMAX 499 int WAVEMIN 7339.0 float WAVEMAX 9915.0 float PSFTYPE GAUSS-HERMITE str PSFVER 3 int ======== ============= ===== ===================== Data: FITS image [float64, 7x500] HDU1 ---- EXTNAME = YTRACE Encodes the Y coordinate of the fiber traces in the CCD. Y is in units of pixels, along the dispersion axis and increases with increasing wavelength. YTRACE is a 2D array of size [nfiber,ncoef]. Each row contains the Legendre polynomial coefficients for a fiber trace. The polynomial applies to a reduced wavelength = (2*wavelength-(WAVEMIN+WAVEMAX))/(WAVEMAX-WAVEMIN) where WAVEMIN and WAVEMAX are header keywords. Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ======== ============= ===== ===================== KEY Example Value Type Comment ======== ============= ===== ===================== NAXIS1 7 int length of data axis 1 NAXIS2 500 int length of data axis 2 FIBERMIN 0 int FIBERMAX 499 int WAVEMIN 7339.0 float WAVEMAX 9915.0 float ======== ============= ===== ===================== Data: FITS image [float64, 7x500] HDU2 ---- EXTNAME = PSF Binary table with the PSF shape parameters encoded as Legendre polynomials of wavelength, per fiber. Each row of the table addresses a parameter. The column PARAM provides its name. The column COEFF contains a 2D array of size [nfiber,ncoef] with its associated Legendre polynomial coefficients. As for XTRACE and YTRACE, each row of the COEFF array provided the Legendre coefficients of a fiber. The polynomial applies to the reduced wavelength = (2*wavelength-(WAVEMIN+WAVEMAX))/(WAVEMAX-WAVEMIN) where WAVEMIN and WAVEMAX are header keywords. The additional columns LEGDEGX and LEGDEGW are the degrees along the cross-dispersion and dispersion axes used during the fit. This format can apply to several PSF models. For the one currently used in DESI, based on Gauss-Hermite polynomials, the parameters are the following: - 'GHSIGX' Gauss-Hermite Gaussian sigma along X - 'GHSIGY' Gauss-Hermite Gaussian sigma along Y - 'GH-I-J' with I and J in the range 0 to 6: Gauss-Hermite polynomial coefficient of degree I along X and J along Y - 'TAILAMP' PSF tail amplitude - 'TAILCORE' PSF tail core size - 'TAILXSCA' relative scaling along X - 'TAILYSCA' relative scaling along Y - 'TAILINDE' PSF tail asymptotic power law index - 'BUNDLE' Index of fiber bundle (or fiber block) - 'STATUS' Not used currently (values = 0) - 'CONT' Value of continuum at this fiber and wavelength PSF(X,Y) = PSF_CORE(X,Y) + PSF_TAIL(X,Y) PSF_CORE(X,Y) = [ SUM_ij (GH-i-j)*HERM(i,X/GHSIGX)*HERM(j,Y/GHSIGY)*GAUS(X,GHSIGX)*GAUS(Y,GHSIGY) PSF_TAIL(X,Y) = TAILAMP*R^2/(TAILCORE^2+R^2)^(1+TAILINDE/2) with R^2=(X/TAILXSCA)^2+(Y/TAILYSCA)^2') Required Header Keywords ~~~~~~~~~~~~~~~~~~~~~~~~ .. collapse:: Required Header Keywords Table .. rst-class:: keywords ============= =========================================================== ===== =============================================== KEY Example Value Type Comment ============= =========================================================== ===== =============================================== NAXIS1 8016 int width of table in bytes NAXIS2 59 int number of rows in table PSFTYPE GAUSS-HERMITE str PSFVER 3 str MJD 0 int MJD of arc lamp exposure PLATEID 0 int plate ID of arc lamp exposure CAMERA r9 str camera ID ARCEXP 0 int ID of arc lamp exposure used to fit PSF NPIX_X 4114 int number of columns in input CCD image NPIX_Y 4128 int number of rows in input CCD image HSIZEX 8 int Half size of PSF in fit, NX=2*HSIZEX+1 HSIZEY 5 int Half size of PSF in fit, NY=2*HSIZEY+1 FIBERMIN 0 int first fiber (starting at 0) FIBERMAX 499 int last fiber (included) NPARAMS 57 int number of PSF parameters LEGDEG 1 int degree of Legendre pol.(wave) for parameters GHDEGX 6 int degree of Hermite polynomial along CCD columns GHDEGY 6 int degree of Hermite polynomial along CCD rows WAVEMIN 5546.0 float minimum wavelength (A), used for the Legendre p WAVEMAX 7835.0 float maximum wavelength (A), used for the Legendre p PSFERROR 0.0 float assumed PSF fractional error in chi2 READNOIS 0.0 float assumed read out noise in chi2 GAIN 1.0 float assumed gain in chi2 B00RCHI2 1.265121999136178 float best fit chi2/ndf for fiber bundle 0 B00NDATA 140488 int number of pixels in fit for fiber bundle 0 B00NPAR 1746 int number of parameters in fit for fiber bundle 0 B01RCHI2 1.244445290488158 float best fit chi2/ndf for fiber bundle 1 B01NDATA 141467 int number of pixels in fit for fiber bundle 1 B01NPAR 1786 int number of parameters in fit for fiber bundle 1 B02RCHI2 1.287672518525548 float best fit chi2/ndf for fiber bundle 2 B02NDATA 142582 int number of pixels in fit for fiber bundle 2 B02NPAR 1802 int number of parameters in fit for fiber bundle 2 B03RCHI2 1.297067743767708 float best fit chi2/ndf for fiber bundle 3 B03NDATA 140419 int number of pixels in fit for fiber bundle 3 B03NPAR 1793 int number of parameters in fit for fiber bundle 3 B04RCHI2 1.28304830748024 float best fit chi2/ndf for fiber bundle 4 B04NDATA 138599 int number of pixels in fit for fiber bundle 4 B04NPAR 1785 int number of parameters in fit for fiber bundle 4 B05RCHI2 1.269246986023668 float best fit chi2/ndf for fiber bundle 5 B05NDATA 136603 int number of pixels in fit for fiber bundle 5 B05NPAR 1778 int number of parameters in fit for fiber bundle 5 B06RCHI2 1.299512103689112 float best fit chi2/ndf for fiber bundle 6 B06NDATA 137571 int number of pixels in fit for fiber bundle 6 B06NPAR 1807 int number of parameters in fit for fiber bundle 6 B07RCHI2 1.347344727978646 float best fit chi2/ndf for fiber bundle 7 B07NDATA 135041 int number of pixels in fit for fiber bundle 7 B07NPAR 1788 int number of parameters in fit for fiber bundle 7 B08RCHI2 1.222211322234266 float best fit chi2/ndf for fiber bundle 8 B08NDATA 130583 int number of pixels in fit for fiber bundle 8 B08NPAR 1737 int number of parameters in fit for fiber bundle 8 B09RCHI2 1.283488581543704 float best fit chi2/ndf for fiber bundle 9 B09NDATA 127868 int number of pixels in fit for fiber bundle 9 B09NPAR 1716 int number of parameters in fit for fiber bundle 9 B10RCHI2 1.275975791937288 float best fit chi2/ndf for fiber bundle 10 B10NDATA 131593 int number of pixels in fit for fiber bundle 10 B10NPAR 1770 int number of parameters in fit for fiber bundle 10 B11RCHI2 1.250307604266956 float best fit chi2/ndf for fiber bundle 11 B11NDATA 133944 int number of pixels in fit for fiber bundle 11 B11NPAR 1778 int number of parameters in fit for fiber bundle 11 B12RCHI2 1.231315819103986 float best fit chi2/ndf for fiber bundle 12 B12NDATA 134637 int number of pixels in fit for fiber bundle 12 B12NPAR 1767 int number of parameters in fit for fiber bundle 12 B13RCHI2 1.238502289060944 float best fit chi2/ndf for fiber bundle 13 B13NDATA 134287 int number of pixels in fit for fiber bundle 13 B13NPAR 1761 int number of parameters in fit for fiber bundle 13 B14RCHI2 1.296845822866915 float best fit chi2/ndf for fiber bundle 14 B14NDATA 139568 int number of pixels in fit for fiber bundle 14 B14NPAR 1818 int number of parameters in fit for fiber bundle 14 B15RCHI2 1.319475598189398 float best fit chi2/ndf for fiber bundle 15 B15NDATA 139759 int number of pixels in fit for fiber bundle 15 B15NPAR 1802 int number of parameters in fit for fiber bundle 15 B16RCHI2 1.2373008163902 float best fit chi2/ndf for fiber bundle 16 B16NDATA 139822 int number of pixels in fit for fiber bundle 16 B16NPAR 1778 int number of parameters in fit for fiber bundle 16 B17RCHI2 1.262409294037498 float best fit chi2/ndf for fiber bundle 17 B17NDATA 140633 int number of pixels in fit for fiber bundle 17 B17NPAR 1770 int number of parameters in fit for fiber bundle 17 B18RCHI2 1.270007569982172 float best fit chi2/ndf for fiber bundle 18 B18NDATA 143004 int number of pixels in fit for fiber bundle 18 B18NPAR 1790 int number of parameters in fit for fiber bundle 18 B19RCHI2 1.275991847448398 float best fit chi2/ndf for fiber bundle 19 B19NDATA 143320 int number of pixels in fit for fiber bundle 19 B19NPAR 1780 int number of parameters in fit for fiber bundle 19 EXPID [1]_ 0.0 float IN_IMAGE [1]_ SPECPROD/preproc/20210508/00087672/preproc-z6-00087672.fits str IN_PSF [1]_ SPECPROD/calibnight/20210508/psfnight-z6-20210508.fits str MEANDY [1]_ 1.53486325871199e-12 float MEANDX [1]_ -0.02150255816129912 float MINDY [1]_ -3.6379788070917e-12 float MINDX [1]_ -0.02509807125352381 float MAXDY [1]_ 1.00044417195022e-11 float MAXDX [1]_ -0.01113212858444967 float ============= =========================================================== ===== =============================================== .. [1] Optional Required Data Table Columns ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. rst-class:: columns ======= ============= ===== =================== Name Type Units Description ======= ============= ===== =================== PARAM char[8] Parameter name COEFF float64[1000] Legendre coefficients[nfiber,ncoeff] LEGDEGX int32 Legendre polynomial degree in the X (Fiber) direction LEGDEGW int32 Legendre polynomail degree in the Y (Wavelength) direction ======= ============= ===== =================== The dimensionality of ``COEFF`` is ``[nfiber,ncoeff]`` where ``nfiber`` is the number of fibers (always 500 for standard production runs) and ``ncoeff`` is the maximum value of any row of ``LEGDEGX`` or ``LEGDEGY``.