PSF (point spread function) files model the mapping of fibers and wavelengths to pixels on spectrograph CCDs.

Naming Convention:

shifted-inputpsf-CAMERA-EXPID.fits, where CAMERA is e.g., “b0”, “r5”, etc. and EXPID is 8-digit exposure number.



File Type:

FITS, 998 KB

See psfnight-CAMERA-NIGHT documentation for a description of the PSF file content.

Four different PSF files are written per camera for each arc lamp exposure:

  1. shifted-input-psf-CAMERA-EXPID.fits: Input PSF with spectral trace coordinates and wavelength calibration adjusted to the current CCD image, used as a starting guess for the PSF shape fit.

  2. fit-psf-before-listed-fix-CAMERA-EXPID.fits: Result of the specex PSF fit before adjusting the PSF model of problematic fibers not included in the fit.

  3. fit-psf-fixed-listed-CAMERA-EXPID.fits: Result of the specex PSF fit with the PSF model of problematic fibers interpolated from neighboring fibers.

  4. fit-psf-CAMERA-EXPID.fits: Final PSF fit (which is the same as fit-psf-fixed-listed-CAMERA-EXPID.fits if there are problematic fibers)

The fit-psf-*.fits files from individual exposures are combined into the psfnight files for each night.

Flat and science exposures have a single PSF file per camera:

psf-CAMERA-EXPID.fits: psfnight file with spectral trace coordinates and wavelength solution adjusted to match this exposure. Flat exposures are adjusted only in x (cross dispersion = fiber direction), while science exposures are adjusted in both x and y (wavelength direction).