Solar Position

BS 8206-2 Section 12.

Date (YYYY-MM-DD)

Local Clock Time (LT)

Latitude (φ°)

Longitude (λ°)

Std. Meridian (λ_s°)

DST (Hours)

Daylight & Luminance

BS 8206-2 Section 2.11.

$L_\gamma = \frac{L_z(1 + 2 \sin \gamma)}{3}$

Luminance at γ ($L_\gamma$):

$\text{DF} = \left(\frac{\text{Illuminance}_{int}}{\text{Illuminance}_{ext}}\right) \times 100$

Daylight Factor ($\text{DF}$):

$\tau_d = \frac{2\pi(J - 1)}{365}$

Day Number ($J$):

Day Angle ($\tau_d$):

$\delta_s = 0.006918 - 0.399912\cos\tau_d + \dots$

Declination ($\delta_s$):

$\text{ET} = 0.170\sin\left[\frac{4\pi(J - 80)}{373}\right] - \dots$

Eq. of Time ($\text{ET}$):

$\text{TST} = LT + \frac{\lambda_s - \lambda}{15} + \text{ET} - \text{TD}$

Local Time ($LT$):

True Solar Time ($\text{TST}$):

$\xi = \frac{\pi}{12}\text{TST}$

Hour Angle ($\xi$):

$a = \sin^{-1}(\sin\phi\sin\delta_s - \cos\phi\cos\delta_s\cos\xi)$

Altitude ($a$):

$g = \cos^{-1}\left(\frac{-\sin\phi\sin a + \sin\delta_s}{\cos\phi\cos a}\right)$

Azimuth ($g$):