Which navigational error increases when a sextant's mirrors are not perfectly perpendicular during celestial observation?

💡 Explanation

When the mirrors are misaligned, instrumental error, specifically side error, arises because the observed celestial body's altitude is consistently skewed due to the angular offset. Therefore systematic errors occur, rather than longitude errors or parallax, which involve other factors like timekeeping and lunar position; or refraction at specific altitudes unrelated to mirror alignment..

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