Diurnal motion all Red circles are Diurnal motion. And its path is known as Diurnal circle of sun.
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Celestial Equator: a blue dot circle.
Ecliptic: a yellow dotted circle.
Ecliptic: orbital plane of Earth around the Sun. Equator tilt and axis tilt of earth and sun are measuring from ecliptic plane.
When we consider that we are at rest and sun moves around the earth along celestial sphere and that path is called Ecliptic and completes one revolution in 365 days and earth completes one rotation in 24h.
J: Intersection of Hour Circle and Celestial Equator.
X: Position of Star.
Ω & ϒ : Intersection of sun’s path and Celestial equator.
Ω: Autumnal Equinox(शरत्काल विषुव )
ϒ: Vernal Equinox(वसंत विषुव )
Coordinate : (α, δ)
α: Right ascension = ϒJ along C.E.
δ: Declination = JX along Hour Circle.
no matter where you live. Ω and ϒ are fixed for all. It is because ϒ and Ω depend only one intersection of Celestial equator and Ecliptic, thus δ and α are fixed for all observer no matter where they live.
If Hour Circle is fixed then it means that the position of the star is fixed. So, ϒ, X, J and Ω are fixed. Hence, α and δ are fixed.
Sun completed one revolution in 230M years. That’s why position of stars do not change in our reference frame.
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