Q:  The Sun has (approximate) absolute magnitude M = +5.
        How many times more luminous is a quasar of absolute magnitude M = -25?


             L (quasar)             -0.4 * ( abs_mag(quasar) - abs_mag(Sun) )
            -------------    =    10 
               L (Sun)   
             
                                    -0.4 * ( -30 )
                             =    10


                                    12
                             =    10



  Q:  The luminosity of the Sun is about L = 4 x 10^(26) Joules/sec.
         What is the luminosity of the quasar?


                                                12
                L (quasar)    =   L (Sun)  *  10


                                        38
                              =   4 x 10        Joules/sec