# Sloan Digital Sky Survey (SDSS) spec file headers

I downloaded spectra from Sloan Digital Sky Survey (SDSS), which has the following column headers flux, loglam, ivar, and_mask, or_mask, wdisp, sky and model (determined by tdump and tprint in pyraf.stsdas).

I know about flux, loglam, sky and model but I wanted to know what are the other headings are and where are they used. ['loglam' is the log10(wavelength)]

Also, is there any way from which I can determine redshift using the SDSS spectra, by not looking on the quasar page.

The answers can be found on the Documentation page:

HDU 1 (extname COADD): Coadded Spectrum from spPlate

Binary table with columns:
Required  Columns
Name      Type      Comment
flux      float32   coadded calibrated flux [10-17 ergs/s/cm2/Å]
loglam    float32   log10(wavelength [Å])
ivar      float32   inverse variance of flux

As for redshift determination from SDSS spectra; you can identify emission line features like e.g. the H$\alpha$ - [N II] triplet around 6700 Å restframe, of the O II 3727+3729 doublet, or the H$\beta$ + [O III] 4959+5007 complex, and dividing their observed wavelengths by their restframe wavelengths.