If the unit is one magnitude, it applies to a star of that faintness, covering (defocused) a solid angle of:

save settings    use my saved settings

Another option is to use your own command line (ev. overriding all previous data):

(`?' gives help).

 will say you, what are the equivalents of the luminance of
 #  cd/m2  (candela per square meter)
LUM m #
 will compute the luminance of a star of # magnitudes defocused to
 one "square minute";
 will do that for the defocusation of
 one "square second",
 for that of one "square degree"
LUM m<diam> #     and similarly for S and D
 will do that for a star defocused to a circle of <diam> minutes diameter.

1999 (C) Jan Hollan, N.Copernicus Observatory and Planetarium in Brno,
 subject to the GNU General Public License,;
 source code available at
 source code available at

The result you got from the programme lum (available as a part of a package (1.2 MB) -- the needed unit str_num.pas is unzipped within this directory, the whole tree of my programmes within this directory) with a command line:

For more info on the queer units in astronomy, see in Czech mainly this paper, in English just a short explanation here (in both cases, the html versions may be not really OK).

For more info on units etc. in general, see The National Institute of Standards and Technology Reference on Constants, Units, and Uncertainty: