!*****************************************************
!*    This program caculates the absolute stellar     *
!*     based on relative magintude and distance       *
!* -------------------------------------------------- *
!* SAMPLE RUN:                                        *
!*                                                    *
!* To calculate absolute stellar magnitude:           *
!* Give relative mag. and distance in parsecs: 10 3   *
!*                                                    *
!* A star with relative magnitude  10.00              *
!* at a distance of   3.0 parsecs                     *
!* has an absolute magnitude of  12.61                *
!*                                                    *
!* -------------------------------------------------- *
!* Ref.: "Problem Solving with Fortran 90 By David R. *
!*        Brooks, Springer-Verlag New York, 1997".    * 
!******************************************************
! Explanations;
! ------------
!   The absolute magnitude M of a star is related to its
! relative magnitude m and and the distance to a star r,
! measured in parsecs, where 1 parsec = 3.26 light years,
! by the equation:
!
!                  M = m + 5 - 5 log10(r)
! 
!   According to this equation, a star with a relative
! magnitude of +1 at a distance of 10 parsecs has an 
! absolute magnitude of +1. The larger the magnitude, the 
! dimmer the star. Sirius is a very bright star with a
! relative magnitude of -1.58. Stars visible to the naked
! eye range mostly from about +1 to +6 in relative magni-
! tude. 
!   The dimmest star that can be seen with the 200-inch
! Hale telescope has a magnitude of about +23.
!---------------------------------------------------------  
Program Starmag

  Implicit None

  Real abs_mag, rel_mag, parsecs

  print *,' '
  write (*,"(' To calculate absolute stellar magnitude:')")
  write (*,"(' Give relative mag. and distance in parsecs: ')", &
         advance='no')
		 
  read *, rel_mag, parsecs
  
  abs_mag = rel_mag + 5.0 - 5.0 * Log10(parsecs)

  print *,' '
  Write (*,10) rel_mag, parsecs, abs_mag
  print *,' '

10 format(' A star with relative magnitude ',f6.2/ &
          ' at a distance of ',f5.1,' parsecs'/    &
          ' has an absolute magnitude of ',f6.2)

End

!end of file starmag.f90