# pvlib.solarposition.declination_spencer71¶

pvlib.solarposition.declination_spencer71(dayofyear)[source]

Solar declination from Duffie & Beckman [1] and attributed to Spencer (1971) and Iqbal (1983).

Warning

Return units are radians, not degrees.

Parameters

dayofyear (numeric) –

Returns

declination (radians) (numeric) – Angular position of the sun at solar noon relative to the plane of the equator, approximately between +/-23.45 (degrees).

References

[1] J. A. Duffie and W. A. Beckman, “Solar Engineering of Thermal Processes, 3rd Edition” pp. 13-14, J. Wiley and Sons, New York (2006)

[2] J. W. Spencer, “Fourier series representation of the position of the sun” in Search 2 (5), p. 172 (1971)

[3] Daryl R. Myers, “Solar Radiation: Practical Modeling for Renewable Energy Applications”, p. 4 CRC Press (2013)