Moon Dials

My saga is set in the city of Palma.
I was reading recently that there are a lot of Moon Dials (as opposed to sun dials) in the city. ... moondials/

I can't find too much online about the uses of these items.

Anyone have any knowledge or references about them? I'm thinking it could be a nice way to use astronomy to discover a vis source or regio.

I've unfortunately never heard of a moon dial before but I must say that's quite cool! I like the idea of finding a regio with one of these, or a vis source. Since they only work during the full moon you could take one of the classics (harvest moon, blue moon, etc.) to draw inspiration for the theme of the regio or the type of vis.

(As a funny aside the university my wife works at has an enormous sun dial next to the central courtyard, however when it isn't incorrect due to day light savings it's usually covered in snow. To add insult to injury the children's museum on the other side of town has a sun dial where you stand at different points depending on the month and it is exceptionally accurate year round, even during day light savings!)