This includes the moon's absolute position, age and phase. For this, the new
simgear MoonPos::get*() functions are tied to the property tree at
"/ephemeris/moon/" using a new tieMoonPos() function.
In addition the moon illumination factor is exposed by tying the simgear
MoonPos::getIlluminanceFactor() function to the /environment/moonlight property.
This is a number ranging between 0 and 1 based on the log of the illuminance of
the moon outside the atmosphere. It is calculated as
factor = (log(I) - max_loglux) / (max_loglux - min_loglux) + 1.0,
The illuminance of the moon outside the atmosphere, I, is from equation 20 from:
Krisciunas K. and Schaefer B.E. (1991). A model of the brightness of
moonlight, Publ. Astron. Soc. Pacif. 103(667), 1033-1039 (DOI:
http://dx.doi.org/10.1086/132921).
For more background, see
http://forum.flightgear.org/viewtopic.php?f=47&t=28201&start=60#p270516 .
Remove uses of .str(), .c_str() and some other methods of SGPath.
Pass SGPath directly where possible, or explicitly convert to the
appropriate 8-bit encoding.
