Celestia Forums

I've been playing with different ways of navigating through space in my script. My first thought was to have a right ascension, declination display. I was thinking I could look up stars and navigate to them using these coordinates. However, I quickly discovered that universal coordinate are offset so I don't get quite the right numbers. But then I realized that this doesn't make sense anyway, because these numbers are only good near Earth even if I allowed for the offset.

Right now I'm navigating by creating a three-dimensional grid system centered at Sol but the problem with that is it doesn't correspond with anything astronomers use (I don't think). I'm thinking maybe Galactic Coordinates? Anybody have any thoughts on this?

Henry

The Galactic coordinate system used by astronomers also is Earth-centered.

I suppose you could use galactocentric galactic coordinates. The necessary transform would involve only a translation of the origin from the more common Galactic coordinate system. It's used often enough when studying objects that orbit the Milky Way. Apparently some astronomers do use "local groupocentric'' or "Virgocentric'' or even the microwave background frame depending on what they're studying.

I think what I really want is a display that shows the observer's orientation with respect to something that makes sense compared to what they can see. Galactocentric galactic coordinates would orient the user to the plane and center of the Galaxy. That's probably a good place to start, but I may want to eventually have several coordinate displays the user could switch to depending on what was going on. (Celestia already provides some of those.)

Is there a description somewhere of the relationship between universal and Galactic coordinates? Or at least the position of the vernal equinox in Galactic Coordinates?


Thanks for your help.

Henry

I found, in Green's Spherical Astronomy, a rotation matrix to convert Equatorial to Galactic coordinates for Epoch 2000. I understand Equatorial changes slowly enough to make this fairly accurate for this time period.

I 'm thinking then I may have the tools but I'm not sure how to implement them in celestia. I want to transform the current orientation into Galactic coordinates so that I know what the orientation is in Galactic. Is it as simple as taking the orientation vector, converting it to Equatorial and then transforming that vector (using rotation:transform) into Galactic?

I guess my basic question is, does this rotation matrix give me enough information to do what I want in celestia?

Henry