The main justification for this proposal is to use the volume and depth of the Sloan Survey to more accurately determine the shape of the Luminosity Function at the bottom of the main sequence and beyond.
Most reports agree that the LF peaks around or .
Fainter than this is where the controversy begins. The recent HST result of Bahcall et al. The SDSS data will provide complete star counts to 300 pc for over 100,000 square degrees to the North Galactic latitudes and even fainter for 300 square degrees to the South. With distance estimates for a large percentage of this data, the Luminosity Function at the faint end of the main sequence should be well established. To accurately determine the LF, the absolute magnitude is needed.