A suitable fixed collector orientation for most purposes is facing the equator (e.g. due north in the southern hemisphere) with a slope equal to the latitude,as in (4.10). Other considerations will modify this for particular cases, e.g.the orientation of existing buildings and whether more heat is regularlyrequired (or available) in mornings or afternoons. However, since cos Ѳ ≈ 1 for Ѳ < 30 , variations of ±30 in azimuth or slope should have little effect on the total energy collected. Over the course of a year the angle of solar noon varies considerably, however, and it may be sensible to adjust the ‘fixed’ collector slope month by month.