Open Thread: Spherical Astrolabe

The major drawback of a planispheric astrolabe is that the projection used to make it flat is different for every latitude. (This is dealt with by having interchangeable plates.) If one doesn't need the astrolabe to be flat, and instead allows it to be spherical, that drawback disappears.

While we have a fair number of documents about spherical astrolabes, this is the only intact one to survive. It was made by someone named Musa 540 years ago, it's about the size of a baseball, and I want one.

While they eliminate the major drawback of planispheric astrolabes, spherical astrolabes have problems of their own. Notably, the fact that only one survives intact should give you some idea of how durable they are, and flat things tend to be more convenient than spheres.

I'm sorry this is late again. I hope you like the picture.


We have special open threads set aside for discussing various movies, said discussions including plain text spoilers.  These are the current ones:
   ● Birds of Prey
   ● Star Wars: Episode IX -- The Rise of Skywalker

You do not need a special open thread to discuss a movie.  Provided you encipher any spoilers (the standard method is by summoning Cthulhu) discussion of movies is quite welcome in the regular open threads.

The special threads are for cases where movie-talk might threaten to drown out other discussion, is expected to take place over multiple weeks, or both.  If you believe a given movie calls for one, simply say so.


Friday Sunday Recommendations!  What have you been reading/writing/listening to/playing/watching lately?  Shamelessly self-promote or boost the signal on something you think we should know about - the weekend’s ahead of us almost over, so give us something new to explore!

And, like on all threads: please remember to use the "post new comment" feature rather than the "reply" feature, even when directly replying to someone else!


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