Exercise:

A star’s true position is
Right Ascension 6h 0m 0s, declination 0° 0' 0".
On the date of the Spring Equinox,
how far will it appear to be shifted by aberration,
and in what direction?

First convert from RA and dec. into ecliptic coordinates.
This star has ecliptic longitude λ = 90°,
and ecliptic latitude β = -ε = -23°26'.

At the spring equinox, the Sun has ecliptic longitude λ_S = 0°
so λ_S-λ = -90°.

Δλ cosβ = -k cos(λ _S-λ) = 0
so Δλ = 0.

Δβ= - k sin(λ_S-λ) sinβ = 0
where k = 20.5" and β = -23°26'.
so Δβ= +8.15".

So star is shifted 8.15" northwards, by aberration.

Back to "aberration".