VGA Demo: sun Declination over the year

Reinhard

/*
 * The declination of the sun is the angle between the equator and a line 
 * drawn from the centre of the Earth to the centre of the sun. 
 * The daily(*) variation of the declination angle 
 * is compute in the program below.
 * (*)from January 1. to December 31.
 * 
 * graphic:
 * the moving sun level is drawn yellow
 * the trace of sun is green
 * and the equator is in white
 * 
 * this can compile w/o changes
 * i.e. for PC gcc -o sun_decl sun_decl.c -lm
 * in this case the declination is print to stdout
 * and can processed further i.e. with gnulot
 * 
 * or/and for the P2
 * fastspin -2b sun_decl.c graphictools.c
 * 
 * it is also an example to design for PC and P2 in C
 * 
*/