Hi There! So far, we have spent a lot of time thinking about equinoxes as a curious layperson looking at sunrises, shadows and daylengths everyday.
Another way is shown in the image below. Imagine a huge celestial sphere co-axial with the earth, with North and South Celestial Poles and a Celestial Equator. All the celestials ( dEvA: ) such as the stars and planets are on this sphere, equidistant from the earth.
The sun’s orbit around the earth defines the ecliptic plane and it is inclined at 23.5 degrees to the celestial equatorial plane. (Because the Earth’s axis is tilted at 23.5 deg to the earth’s orbit around the sun).
The points of intersection between the ecliptic plane and the equatorial plane are the Equinox.points.Equinoxes occur when the Sun passes through these points.
dēvēndra, is the vernal equinox point and is true East. The other dēvā: are the nakşatrāņi, tārā: and grahā: . The word dēva is related to diva or light and divya or divine, in samskŕtam.
When Aditya (sUrya) meets indra we have a spring equinox!!