astLib usage

[razman786]

From https://github.com/razman786/tigger_py5/issues/84#issue-838004745

from @o-smirnov:

Let's make a mental note to look at the use of astLib again. There has been substantial churn around it since I first plugged it in. I think it was incorporated into astropy, plus there's some overlap with astropy's WCS functions. I think it might be possible to simplify and modernize this bit of code.