Which optical effect limited early astrolabe accuracy when sighting stars near the horizon?

💡 Explanation

When sighting stars near the horizon with an astrolabe, atmospheric refraction occurs because the density of the Earth's atmosphere increases, causing light to bend and alter their apparent position. Therefore, atmospheric refraction limits accuracy, rather than aberrations or diffraction effects which were less significant with naked-eye observations.

• Which outcome occurred when Roman siege engines launched projectiles at city walls built using opus caementicium (Roman concrete)?
• Which structural vulnerability increased for late Roman fortifications that incorporated extensive mortar use during construction?
• Which outcome occurred if Bronze Age Mesopotamian chariots exceeded copper's fatigue limit during warfare use?
• In the design of historical astrolabes, which consequence resulted from inaccuracies in stereographic projection?
• Which risk increases when poorly maintained terraces experience prolonged rainfall on the Andes mountains?
• Which mechanical consequence resulted from rapid catapult arm deceleration upon projectile release during Roman siege warfare?