Arthur,
In the portion of my earlier message below, I gave a rather poor account.
Instead: The Moon perturbs the Earth relative to the barycenter causing a
difference between the arrival times of Perihelion for the Earth/Moon
barycenter and the actual Earth. The Perihelion of the Earth/Moon barycenter
is almost constant, yet the Earth's is not. Sorry!
Lastly, independent of this large scale variation, Perihelion during the
period 1980-2020 is shifting (eastward) at 12 arc-seconds per year. I hope
that does it.
Best Regards,
Luke Coletti
Luke Coletti wrote:
> The variations listed are mainly due to the perturbing effects of the
> Moon as the barycentric point of the Earth/Moon system changes, see J.
> Meeus, Mathematical Astronomy Morsels, chap 27.
