Since

    1  degree       =   60  arc-minutes

    1  arc-minute   =   60  arc-seconds


  it follows that
                                           
    1  degree       =   60 arc-minutes *  (60 arc-seconds per arc-minute) 

                    =   3600 arc-seconds


  The Moon is about 0.5 degrees across, or 1800 arcseconds.