# Sun-Coefficient simulation of 5-phase method

Hi all,
As for the sun-coefficient simulation part of 5-phase method, the annual sky-matrix is generated as follows:

``````gendaymtx -m 6 -5 0.533 -of assets/NYC.wea > skyVectors/NYCd6.smx
``````

where -m 6 means 5185 subdivisions of sky and the term -5 0.533 indicates that the sky-matrix is being generated for the Five-Phase Method. The value of 0.533 corresponds to the size of the solar disc. How to calucate this value 0.533?
So there is a question: when m is other number like 1, and the subdivisions are 145, so how about the corresponding size of solar disc? I guess the value should be larger than 0.533. And what is the relationship between the m and the size of the solar disc?
Any help or advice is appreciated!

The subtended solar angle is 0.533 degrees measured from Earth’s orbit, and this doesn’t (and should not) change with the -m setting. It is there to normalize the solar radiance to its true value, rather than spreading it over the solid angle of the sky patch as gendaymtx would do without the -5 option. (In fact, it normally spreads the sun over the 4 nearest patches.) The reasons behind it are specific to the handling of the solar position matrix in the 5-phase method.

Hi Greg,