Exercise:
The coordinates of the Galactic
North Pole are given officially as
α
= 12h49m00s, δ = +27°24'00",
relative to the equator and equinox of 1950.0.
What should they be,
relative
to the equator and equinox of 2000.0?
(For this calculation, take the
values of m and n for the year 1975:
m = 3.074s per year;
n =
1.337s per year = 20.049" per year.)
The formulae are:
Δα
= m + n sin(α)
tan(δ)
Δδ
= n cos(α)
Substitute the coordinates
given in the question:
α1950
= 12h49m00s = 192.25°,
δ1950
= +27°24'00" = 27.40°,
to get
Δα
= 2.927s per year, or +146.348s in 50 years.
Δδ
= -19.59" per year, or -979.63" in 50 years.
Add these to the 1950 values of
α and δ,
to get
α2000
= 12h51m26s
δ2000
= +27°07'40"
Back to "precession".