Does the atmosphere magnify the Moon near the horizon?

No. The Moon's striking enlargement near the horizon is a perceptual illusion, not atmospheric magnification.

NASA explains that photographs taken with unchanged zoom settings show essentially the same lunar width near the horizon and higher in the sky. Atmospheric refraction can slightly flatten its outline instead. Michael Bach's visual demonstration independently distinguishes perceived enlargement from actual size.

The full explanation of the illusion remains unsettled. Proposed mechanisms involve how we judge distance and size. That uncertainty does not mean the atmosphere acts as a magnifying glass.