Celestia Forums

Hi there,

the question i want to ask is:
What is the RA and DEC to the position of the center of our galaxy?

I went trough some websites and got all different answers. If i have the things right in my brain (not necessarily so, since i just started with astronomy) is the RA and DEC counted from the vernal equinox. So the direction should be more or less stable, or am i wrong here?
I know the sun is moving too, but does this really matter much?

Anyways, i hope someone can help me with my original question.

It depends which "centre of the galaxy" you want, and in which coordinate system, which is probably what's creating your confusion.
The zero point of galactic latitude and longitude was defined in B1950.0 coordinates, but the precession of the equinoxes means that those coordinates have changed in J2000.0 coordinates. Also, this "centre" was defined before we had knowledge of the real objects at the centre of the galaxy, so you'll find that Sgr A* (which I recall is associated with the central black hole) doesn't lie at the galactic coordinates (0,0).

So do you want to know the RA and Dec of the centre of the galactic coordinate system, or the RA and Dec of the central black hole?

Grant

Hi grant,

could you be so kind and give me the RA and Dec for both?

I need the one for the central black hole, but if i also have the other coordinate set,i will know which is which and will be able to position my star system correctly, plus/minus the usual tolerances

Guckytos

Sgr A* is at RA 266.416854, dec -29.007750. The zero point for galactic lat and lon is at RA 266.404996, dec -28.936172. Both in J2000.0 coordinates.

Grant

Thanks grant,

two more questions.
Does this mean i have to tell Celestia somehow to use those J2000.0 coordinates if i want to place a solar system on a direct line to Sgr A*?
How do i do it, by placing an Epoch J2000.0 line in the stc-file?

Ah the guest above, that was me.
Had forgotten to log in.

Btw: the login is a bit strange. I must always log in two times before the sstem recognises me. Is this normal?

Anonymous wrote:Does this mean i have to tell Celestia somehow to use those J2000.0 coordinates if i want to place a solar system on a direct line to Sgr A*?

No, it's OK, those are the coordinates used by Celestia's stars database, so if you plug these numbers directly into an stc everything will be internally consistent. (But you won't be able to place a star as far away as the galactic centre, since Celestia doesn't currently plot stars beyond 16000ly.)

Grant