Am Sun, 12 Apr 2009 19:05:55 +0200 schrieb Jörg 'Yadgar' Bleimann:

> High!
> 
> Lukas Winter schrieb:
> 
>  > Why not do these calculations in cartesian coordinate space? I
> suppose you already have a way of converting a point from earth's local
> geographical coordinate system to earth's local cartesian coordinate
> system.
> 
> No, I do not yet... how could I do this?
> 
> See you in Khyberspace!
> 
> Yadgar

So... wait, you have a "full-fledged POV solar system" and no way of 
converting coordinates? How can you place _any_ object if you do not have 
cartesian coordinates which POV uses everywhere?
Take a look at chapter 3 of the tutorial, there the author describes how 
to convert geometric and cartesian coordinates.
The author of this tutorial calculates everything in respect of an 
observer on the surface of the earth which I think is the traditional 
astronomic approach but could pose some difficulties in POV. If you have 
already followed this tutorial all along then it would be nonsense to 
abandon this way of calculation.
So, how do you for example place the sun? Do you do something like...
object
{
  sun
  translate z*suns_distance_from_earth
  rotate x*suns_latitude_viewed_from_earth
  rotate y*suns_longitude_viewd_from_eart
} ?
I think the tutorial suggests doing that but it makes everything 
extremely complicated. No wonder the geocentric model is no longer used...
Sorry, I can't come up with an answer to your original question without 
knowing how you set up your coordinate system.

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