# Euler rotations in galactic plane to change to equatorial

1. Jul 16, 2010

### birdhen

HI there,

I am having problems understanding something.
If I have an axis pointing towards the galactic north pole, and I rotate it using an Euler rotations how can I can I establish the rotation angles needed so that it will be pointing to the equatorial North pole.
I am looking for values alpha and beta where alpha can run from -pi-->pi and beta can run from -pi/2-->pi/2.

Many thanks

2. Jul 16, 2010

### phyzguy

3. Jul 16, 2010

### birdhen

Thank you for your reply. I am getting confused still. Would the galactic north pole just have l=0 b=90 in galactic coordinates? I am imagining the surface of a sphere, if b=90 is the top point of the sphere, then there can be no l value as the horizontal plane through the sphere would just be a point.

4. Jul 16, 2010

### phyzguy

These types of coordinates systems have a singularity at the poles, so the north galactic pole has coordinates (L=anything, B=90). The same is true on the Earth. If the latitude is 90 degrees, it doesn't matter what the longitude is, you are at the pole.

5. Jul 16, 2010

### birdhen

OK , of course, thanks !