# Angles on the celestial sphere

1. Mar 2, 2006

### Zaphodx57x

Given the right ascension and declination of two objects in the sky. Is there a way to calculate the angle between them?

If so, do right ascension and declination need to be converted to radians or can they retain their units?

2. Mar 2, 2006

### matt.o

the formula to measure the angle between 2 objects on the sky given their positions is;

$$\cos\theta = \cos{\delta_1}cos{\delta_2}\cos(\alpha_1-\alpha_2) + \sin{\delta_1}\sin{\delta_2}$$

where $$\delta_1$$ and $$\delta_2$$ are the declinations in degrees or radians and $$\alpha_1$$ and $$\alpha_2$$ are the right-acsensions in radians or degrees.

Last edited: Mar 2, 2006
3. Mar 5, 2006

### Zaphodx57x

Thank you much.