Which function did the 'tympanum' or 'mater' disk primarily serve within the intricate mechanics of a medieval astrolabe?

💡 Explanation

When multiple altitude plates are necessary in astrolabes the mater provides physical support, because this avoids building the frame onto specific nonvariable scales. Therefore, changeable altitude coordinates become possible, rather than universal projection, measurement or atmospheric corrections, which use different parts of this navigational device.

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