The astrolabe is a tool that copies the sky spread overhead onto a flat disc. The mater holds the whole thing, the tympan is engraved with the horizon of the observing site, and the pierced rete overlays it as the rotation of the sky itself.
Basics: James E. Morrison, The Astrolabe (an overview of the projection and the role of each part).
Look only at how the three discs stack, and tell which one moves and which ones do not.
Observation Story
See the whole of folding the sky onto one disc, with the mater, tympan, and rete stacked.
Sprawdzenie odkrycia
Which part carries the rotation of the sky on an astrolabe?
Astrolabe: A Tool for Measuring the Sky - Luneidea
