Armillary sphere ring.
https://diqn32j8nouaz.cloudfront.net...ary_sphere.jpg
Full size Armillary sphere. 3:42 video:
https://www.youtube.com/watch?v=AaWuJHQL-bQ
More: https://en.wikipedia.org/wiki/Armillary_sphere
Previously:
https://www.homemadetools.net/forum/...713#post102271
https://www.homemadetools.net/forum/...960#post125012
https://www.homemadetools.net/forum/...240#post116051
https://www.homemadetools.net/forum/...340#post116509
https://www.homemadetools.net/forum/...2674#post76760
