GNUMAGIC is a fast eigenvector hybrid look-up table method for the calculation of 
global and direct irradiance. MAGIC contains a interface for satellite based cloud 
information provided by the Heliosat meethod.  
Libradtan has been used to develop GNUMAGIC, in detail for sensitivity studies 
and the calculation of the look-up tables. The software including documentation 
is available at:

http://gnu-magic.sourceforge.net or 
http://sourceforge.net/projects/gnu-magic