  The goal of this document is to illustrate that teaching the concepts of
magnitudes is a needless complication in introductory astronomy courses, and
that use of monochromatic luminosities, rather than arbitrarily defined
magnitudes, leads to a large gain in transparency. This illustration is done
through three examples: the Hertzsprung-Russell diagram, the cosmic distance
ladder, and interstellar reddening. I provide conversion equations from the
magnitude-based to the luminosity-based system; a brief discussion; and a
reference to sample lecture notes.
  I suggest that we, astronomers in the 21st century, abolish magnitudes and
instead use (apparent) monochromatic luminosities in non-specialist teaching.
Given the large gain in transparency I further propose that we seriously
consider using (apparent) monochromatic luminosities also in research papers,
bringing optical astronomy in line with astronomy at other wavelengths.
Comments are welcome.
