pub fn angular_separation(a: [f64; 3], b: [f64; 3]) -> Result<f64, AngleError>Expand description
On-sky angle (degrees) between two direction vectors, via the stable
atan2(|a x b|, a . b) form.
Vectors need not be normalized, but each must be finite, non-zero, and have
a finite positive squared norm under dot3. Extreme magnitudes whose squared
norm overflows to infinity or underflows to zero are rejected with
AngleError::InvalidInput. Fields "a" / "b" identify the offending
argument.