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data_reduction [2013/09/05 22:25]
mjc [Flux Calibration] 		data_reduction [2013/09/06 03:06] (current)
mjc [Flux Calibration]
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 ==== Flux Calibration ==== ==== Flux Calibration ====
-links to stdstar catalogs...+After WiFeS data have undergone standard image processing steps (e.g., bias subtraction, cosmic ray rejection, flat-fielding), the absolute flux scale of the data must still be assessed.  This is done by observing spectrophotometric standard stars and comparing their observed fluxes to reference spectra.  In PyWiFeS this is done with the procedure outlined schematically in the Figure below, using routines defined in the 'wifes_calib' sub-module.
  
 {{ :wiki:flux_cal_wifes.png?600 |}} {{ :wiki:flux_cal_wifes.png?600 |}}
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 +The flux calibration step corrects for the smooth instrument throughput curve, as well as atmospheric extinction.  However sharp absorption features caused by molecules in the atmosphere (primarily O<sub>2</sub> and H<sub>2</sub>O) remain, and must be corrected in object spectra (bottom panel below) by measuring their structure in the spectra of flux-calibrated smooth spectrum stars (top panel below).
  
 {{ :wiki:telluric_wifes.png?400 |}} {{ :wiki:telluric_wifes.png?400 |}}
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