Hermetic Astrology on other planets

[Inky]

I'm not sure about any of the following.

Planetary days, and the planetary hours they're based on, are, as far as I can tell, completely arbitrary and don't correspond to anything that's happening astronomically with that particular planet. And if it went by Martian days and hours that were divisions of a Martian day, then they'd rapidly get out of step with planetary days on Earth, as the Martian day is a slightly different length. So if there weren't already mages on Mars who'd found out, then when you arrived you'd have no way of telling which planetary day it was on Mars except trial and error - if you were using them at all, the GM would have to make a note of what planetary day it was but not show the players.

That's assuming that you're just using the same set of planets as you would on Earth, because if you're not then, as previously discussed by various people, things get even messier and I don't honestly think there's any logically coherent way of sorting it out since the sequence of planetary days on Earth isn't logically coherent anyway in astronomical terms but the rules assume that it's valid.

Originally Posted by dataweaver

And those are adapted from Cabal.

If I were doing this, I'd probably draw inspiration from C.S. Lewis's “The Discarded Image”. Earth is the center of the model, but also the “bottom” of it — a place that's insignificant with regard to the music of the spheres. The Moon serves as the barrier between Earth and the Heavens; and that would remain true even from a Martian colony — the only real difference being that the Martians would be looking at that divide from the outside, and would see Earth isolated by the Moon and silent, contributing nothing but serving as a receptacle for the influence of the planets. No other planet has something like the Moon drawing a boundary between them and the Heavens; rather, the rest of the planets are inherently part of the Heavens.

That said, every planet, including the Earth, has an Intelligence associated with it. For the Earth, that Intelligence is Fortune; and a case could be made that the reason why the influences of the other planets take the form of guiding people's destinies on Earth is because they get filtered through that self-same Fortune. In and around the other planets, the influences would be different in nature, reflecting the nature of a given planet's guiding intelligence. On Mars, that fishing Intelligence is in charge of the martial spirit; and influences from other planets would be felt through that lens: Venus, for instance, would influence Mars by reinforcing the “Band of Brothers” aspect of the martial spirit: the camaraderie that comes from putting your life in your fellow warriors' hands and doing the same for them; the jovian influence on Mars would take Jupiter's role as the King of the planets and would translate it to generals; Mercury's role would translate to scouts; Sol's influence, which on Earth manifests with regard to fortunes pertaining to scholarship, would on Mars emphasize the art of war and martial arts: violence as an art form. And Saturn's influence on Mars would be to play up the toughness of a soldier and the willingness to put it all on the line to achieve the objective.

That's a great idea. This is supposed to be 'Hermetic Astrology' and it's difficult to have 'as above, so below' if you can't unambiguously define 'below'! As fun as considering how, if astrology works, it would work on other planets in realistic astronomical terms is, the rules for this particular magic system assume that we're going by that old mathematically tidy mediaeval model, so sticking to it might give better results.

That'd mean that the planetary days would be the same as those on Earth without having to worry about which planets or Mars's day being a slightly different length.

Logically the place whose sunrise would be relevant is the place Mars is currently directly above on Earth, as if your position is 'Earth but very, very high in the sky' - although perhaps not, as that would be a swine to calculate in play in practice, I'd even have to think carefully about how to set up astrology or astronomy software to do it, as you'd be sort of working backwards. It would also probably lead to the sequence of days being all weird, with Earth's rotation relative to Mars meaning that the 'planetary days' weren't all the same length as seen from Mars and maybe even went back and forth.

I found this amazing site https://www.solarsystemscope.com/ and played with it a bit, but couldn't work that out at all.

Unless your players like playing with astronomical calculations, this probably isn't a good plan in play. You could tidy it up by saying that for some made-up reason to do with the laws of sympathy and contagion, you use the planetary days (and any other location-specific things) of the point you took off from.

I'm not sure how the 'filtered through the lens of the martial spirit' thing would work if you wanted to cast spells about anything other than fighting. Or is the idea that you can only cast spells about fighting?

Originally Posted by malloyd

Alternately perhaps all mortal magic depends on being in the terrestrial realm where there is a mixture of the classical elements (or decanic influences or whatever), and as soon as you leave the sphere of fire and enter the ether of the celestial realm, it all fails. Everything in the Heavens is deterministic and set by God. You simply can't cast spells on Mars (or anywhere outside the innermost edge of the lunar orbit). At least not without Divine Intervention, in which case they do whatever God wants them too.

Edit: for that matter, everything being deterministic, maybe you can't even [want] to cast spells in the Celestial Realms. If the motion of the heavens are entirely controlled by God and themselves forecast everything, you may no longer possess free will should you enter them, lest your actions somehow alter the future by changing said motions.

Maybe humans are made of a different kind of matter and are Insubstantial with respect to Mars, and maybe can't even cast spells on it at all rather than at the usual penalty for being Insubstantial, but can still cast spells on each other and, if any of them know any spells with a long enough range, on Earth. However, if the OP is asking about mages on Mars that suggests that they have in mind being able to adventure fairly normally on Mars.