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Lisa,
Thank you for your explanation.
But what does this have to do with the stereographic projection?
(This was my question). You seemed to mention such connection
with a reference to Ptolemy in your first message on Hyppatia.

As I understand from your description, this was not only
a measuring instrument but also a star almanach and
an (analog) computer in one device. The pictures I see in my books
do not correspond to your description completely.
I suppose there were different types of Astrolabia.

Was this "rete" a stereographic projection of the Celestial
sphere??

Alex.

> PS I know a man in Tasmania who builds workable Astrolabes,
> however this
> is for the Northern Hemisphere only,
> so I've never been able to ever
> actually use one.

I've seen some astrolabia(s) (ae?) on the web.

In  the usual navigation equipment stores.
Made of plastic and cardboard.
Maybe not so nice as the ones handcrafted in Tasmania,
but I believe they are workable.
Don't know about Southern hemisphere, but I can find the
web references for you.

   

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