Which effect caused inaccuracies with medieval Islamic astrolabes tracking distant stars near the horizon?

💡 Explanation

When tracking stars near the horizon in the medieval Islamic period, atmospheric refraction caused bending of the starlight because denser air near the horizon changes the light's path, shifting the apparent star position. Therefore, atmospheric refraction resulted in inaccuracies, rather than expansion, defects, or parallax which require different physical mechanisms or observational setups to have significant impact.

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