Fantastic article, Jacob!

You really got me going...😄

About the only thing that might have slightly improved your article would be the addition of an illustration something like this:

I had to sketch that one out to clarify in my own head why, on a spherical Earth, Polaris is not visible past the equator...

So I haven't bothered to run the numbers, but here's my off-the-cuff analysis:

Polaris is huge... some 44 million miles in diameter, and so in the above illustration, I've shown it to be vastly larger than Earth. And have we noted that--apart from gravitational bending so small as to be of none effect in this example--light travels in a straight line?

However--for perspective--Polaris is also really, really far away. Consequently, light that reaches us--even from the furthest limbs of the star--comes in at a very, very steep angle. For all practical purposes, the incident angle with respect to our equator is going to be ~90 degrees...

The result is that, other than for effects you've already mentioned (atmospheric refraction and attenuation), everything past the equator is in Polaris' shadow.

Thanks for a fascinating article and for stimulating a bit of thinking.🙏 Keeps my brain lubed...

😄😇😉