Throughput Format

HDU EXTNAME=THROUGHPUT

binary table with columns:

  • wavelength[nwave] Wavelength in Angstroms, or loglam[nwave] for log10(Angstroms)

  • extinction[nwave] Atmospheric extinction in mags/airmass; Atm throughput = 10^(0.4 * extinction * airmass)

  • throughput[nwave] Telescope, fibers, spectrographs, and CCDs

  • fiberinput[nwave] Geometric loss at input of fiber for point source.

Required keywords in same HDU EXTNAME=THROUGHPUT (not HDU 0)

  • EXPTIME: Standard exposure time in seconds

  • EFFAREA: Effective area of mirror, including obscuration effects, in cm^2

  • FIBERDIA: Fiber diameter in arcsec

Note: The throughtput format currently does not support per-fiber throughput.

Note: fiberinput in general depends upon source size, seeing, and fiber position misalignments. The default is for for perfectly centered point sources. The format currently does not support extented objects (the user can mimic this though the input spectra provided to Specter.)

The various forms of throughput affect different types of sources:

             OBJECT   SKY    CALIB
EXTINCTION    yes     yes     no
FIBERINPUT    yes     no      no
THROUGHPUT    yes     yes     yes

CALIB = calibration lamps or laser systems mounted with the telescope, i.e. not experiencing sky absorption.