Re: astronomical Beltane

The Tri-Spiral, or the Triskelion, is one of humanity's oldest and most
beloved symbols.

https://www.newgrange.com/newgrange/tri-spiral.jpg 

In tandem with Kerbstone 15 or the sundial stone, it is a wonderful
reminder that geometry ever renews itself across all those thousands of
years.

https://sketchfab.com/3d-models/kerbstone-15-knowth-91f39cf29b564991a6ceb810a10afdb9

The anchor for the day is noon, where the length of time from sunrise to
noon is symmetrical with the length from noon to sunset. Noon remains
common throughout the seasons, so although the declination above the
horizon may change along with the times from sunrise to noon, the anchor
for noon and the 24-hour day remain fixed to each other outside the natural
variations in the total length of the noon-to-noon cycles.

Beltaine and Lughnasadh represent seasonal milestones relative to noon and
the June Solstice, just as the March and September Equinoxes do