We have a considerable background in Astronomical software and are in the process of bringing it to this website. Much of this software demonstrates the dynamic nature of the celestial sphere and we believe that seeing the dynamic behaviour of the celsetial objects is very instructive.
Our astronomy suite is based on the book "Astronomical Algorithms" by Jean Meeus, published in 2009. Our application software uses the full VSOP87 theory coefficients that are published on the web by Jay Tanner at neoprogrammics.com. For our website, however, we have truncated the series as directed in Jean Meeus' book and although positions of the Moon and Planets are accurate to a "few seconds of arc" they should not be relied upon if extreme accuracy is required. Our aim is to produce interesting dynamical explanations of the behaviour of the Moons and Planets in the Solar System.
We have also simplified our main suite is another way by removing correction for precession. Our tests show that you will see "very accurate" behaviour of our models for the period 2015-2035 but decreasing accuracy outside this period. Whilst doing this we also limited "Delta T" to a single value that is representative of its value in 2021. It does not vary from this value by more than 10 seconds of time in the years between 2015 and 2035.
We hope that you find the web pages that are reachable from the menus to the left enjoyable.