DanRyanIrish

Here's a thought. From my understanding, HPC is undefined when the observer lies on the infinite line containing the solar rotational axis. This is because the Sun's centre and rotational...

Ah right. So that's what gimbal lock is! I don't know if this is implemented, but presumably one could define a projective coordinate system wrt to the rotational axis of...

Come to think of it, this is effectively the same as what you said about HGS but less constrained.

Hi all (including @ayshih). As requested, I have transferred the above text to [this google doc](https://docs.google.com/document/d/15-7jkyt_2xiUn-BXVib_aCiFKrSFtWSjUqbV63Cmm6s/edit?usp=sharing). Please comment there for easier discussion.