The 1971 Spencer formula (based on a Fourier series) is also discouraged for having an error of up to 0.28°.
正弦函數的值逼近本身的值，導致的誤差達到0.26度，這讓使用者很沮喪，因為不能在太陽能的領域中使用 The 1971 Spencer formula (based on a fourier series) is also discouraged for having an error of up to 0.28 degrees.。