<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"> Hello everyone, <br><br>I need to calculate solar altitude for 2008, from 6.15 to 18:00 every 15 minute step, and use this information to calculate the direct normal irradiance and together with diffuse irradiance (I have direct and diffuse irradiance values) as an input for PEREZ model using RADIANCE.<br><br> I wanted to ask if RADIANCE can provide me with this information, so a list of sun altitude for a year-based. <br><br>I have seen some website where I can calculate the sun altitude for a single step, however I need the data for a year-based, and it is not a good idea to calculate it each time step. <br><br> If not, can someone provide me with some sources (formulas) how to calculate the values?<br><br>I thank you in advance, <br><br>Best Regards, <br><br>Sokol Dervishi, <br><br><br><br><br></td></tr></table><br>