Which mechanism caused inaccuracies in early Islamic astronomical observations using astrolabes during zenith measurements?

💡 Explanation

When sighting stars near the zenith using an astrolabe, atmospheric refraction occurs because the air density varies with altitude, bending the light path and causing inaccurate angle measurements. Therefore, atmospheric refraction causes error, rather than fatigue, composition, or magnetic effects which are less significant in zenith telescope measurements.

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