June 13, 2005

The file dr3_lya.fits.gz is a fits binary table with 3492 QSO spectra
included in the SDSS DR3 data release.  The flux has been corrected with the 
latest spectrophotometric calibrations from David Schlegel, in spec2d v5_0.
The redshifts of the QSO emission are recalculated to not be skewed by
strong absorption on the blue wing of Lyman-alpha emission.

The file can be read in IDL with

dr3 = mrdfits('dr3_lya.fits.gz', 1)

The inverse variance has been corrected with a correction factor with
a fitting formula from Kristin Burgess:

corrected  Inverse variance =  original Inverse variance/correction

if (original inverse variance > 102.86) then 
  correction =  0.9323 + 1.168/sqrt(original inverse variance)
else
  correction =  1.0474


the wavelengths are spaced in 0.0001 d log_10 Angstroms, or

for i=0,Npix-1 do wave[i] = 10^(loglam0 + 0.0001*i)