Aside from rotation, there is another invariant between the two sets which is much simpler to calculate and allows it to become a matching problem. I think it's worth pointing this out because it is really possible on this kata to get lost in linear algebra.

I have some questions regarding this kata, but first let me say I am intrigued. I see the catalog array item matches the star array items on the answer. I have looked up the unit sphere, and 'think' I understand the conversion of the RA/DEC to the decimal, though I have not yet found how to perform this conversion mathematically or programmatically (obviously). Looking up the RA/DEC was quite interesting, as I have no background in astronomy yet love space things.

Can anyone point out where I might begin to do the background research and study to solve this kata? I am fascinated...