In astronomy , absolute magnitude is the apparent magnitude , m , an object would have if it were at a standard luminosity distance away from us , in the absence of interstellar extinction . In astronomy , to derive absolute magnitude from the observed apparent magnitude of a celestial object its value is corrected from distance to its observer . The absolute magnitude then equals the apparent magnitude an object would have if it were at a standard luminosity distance ( 10 parsec ) away from the observer , in the absence of astronomical extinction .