what is sdss
DR13 Highlights. Data Release 13 (DR13) is the first data release of the fourth phase of the Sloan Digital Sky Survey (SDSS-IV). DR13 contains SDSS observations through July 2015. DR13 includes the following: Optical spectra of galaxies and quasars from the SDSS component Baryon Oscillation Spectroscopic Survey (BOSS), as part of the Sloan Extended Quasar, ELG, and LRG Survey (SEQUELS)