Re: [Celestia-developers] Ideas for 1.5.1 and 1.6.0 features

[Chris L. <cl...@gm...>]

On Jan 23, 2008 1:03 AM, Fridger Schrempp <fri...@de...> wrote:
> Chris,
>
> I rather diagree with your formulation of the emphasis in the coordinate
> display paragraph:  namely the agreement on /observer/ based coordinates.
>
> +++++++++++++++++++++++++++
> Please specify ONE good ///physics/// argument, why we should use observer
> coordinates instead of coordinates with STANDARD, FIXED origins typically
> based in the respective neighborhood of the observer: geocenter, heliocenter,
> barycenter of sol system, galactic center...
> +++++++++++++++++++++++++++

Because observer coordinates can be useful--more useful than
geocentric coordinates for the positions of Earth-orbiting spacecraft
and the Moon. I *don't* think we need to provide observer centered
coordinates for any random position in space.

> At least one of these coordinates should always been displayed as well if you
> prefer observer centered coordinates. If I read your paragraph, it seems
> nothing at all came out of my long mails to you ;-)

I don't disagree with with this.
>
>
> Also in your list of coordinates: galactic coordinates were missing.

That was an oversight, as I just implemented a J2000 equatorial to
galactic coordinate conversion function yesterday. Which brings me to
a question: what is the standard galactic coordinate system? I've seen
a few apparently conflicting definitions; I think the values that I
have are referred to the 1950.0 epoch. Does Wikipedia have it right?
http://en.wikipedia.org/wiki/Galactic_coordinate_system

--Chris