Celestonautics.

From: Alex Ferguson <abf_at_interzone.ucc.ie>
Date: Tue, 13 May 1997 00:40:35 +0100 (BST)

I sit corrected by Nick Brooke on my tentative recollection that:
> > Nick assumed for purposes of his Ephemeris program that
> > the moon shows a constant sized disk all over Glorantha,

> Actually, the Ephemeris only shows stars from one (undetermined) location;

Oh well. I'm sure I saw a comparison of the disk sizes of sun, moon, and planets someplace, but am now quite unable to recall where. Of course, that could have been (implicitly or explicitly) relative, too.

> Roll on the first 3D continental model of Glorantha
> so we can sort out all these questions.

Well, we first have to have a working model of the Moon's apparent "height", whether or not it's Material, Magical, or just Silly. I posted a purely hypothetical suggestion a while back, hoping to provoke a firestorm of counter-speculation, but to little avail. We have one bid of "60 degrees altitude inside the Lunar Empire, much lower elsewhere"; any other takers?

If Steve Martin's right about the parallax of stars and fixed bodies (and my intuition agrees with him, FWLTW), then it seems that the only likely uses of the Sky Dome for navigation are:

	o  Getting a bearing on north (or other preferred compass point)
	   from one of any number of bodies;

	o  Observing the Red Moon to give the direction of the Crater
	   (or I think it's tacticly assumed, anyway);

	o  Spotting Zenith may give an observable parallax for wherever
	   it's hovering over.  (Slon?  I forget where it is in the sky.)

It seems an open question as to whether any sort of "latitude" or "longitude" is measurable directly from the sun (or stars). (This is a separate issue from solar/stellar parallax, note.) The latter would be impractical anyway, for all but the Mostali. Presumably fans of either Round Gloranthas or Bendy Light ought to believe in the principle, though.

Heavenly,
Alex.

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