These constant macros system variables are used in astronomy and astrology macro functions, to provide an easier way to refer to planets than using their numerical IDs.
Thus, instead of the following line of code,
PlanetsNearOn(nRunDate, nSourceIndex, 2, 4)
you can write the following which is easier to write (and more obvious to read later):
PlanetsNearOn(nRunDate, nSourceIndex, n_MERCURY, N_MARS)
The planets are specified using a numerical index, as found in the table here, and where the indices 0 to 9 (Sun to Pluto) can be replaced by a variable made up of n_ followed by the name of the body in uppercase (for example n_MOON).
See also: planetary events ids.
Topic 177625, last updated on 18-Apr-2020