How is the constant "284" derived within the Solar Declination Angle equation?

The earth's axis results in a day-by-day variation of the angle between the earth-sun line and the earth's equatorial plane called the solar declination $\delta$. This angle may be estimated by the following equation [6]: $$ \delta = 23.45° \sin\left[\frac{360°}{365}(284+N)\right], \tag{2.1}$$ where $N =$ year day, with January 1 $+ 1$.

from ScienceDirect Topics: Solar Declination


This is to get the correct phase, so that for $N=81$ (which is March 21, the March equinox) the result will be $\delta=0$, as shown in the graph below.

enter image description here

Image from REUK.co.uk: Solar declination


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.