The angular size barely changes during one night
A rising Moon can look enormous beside buildings or trees, then seem to shrink as it climbs. Photographs made with the same lens show that its angular diameter remains almost unchanged. Atmospheric refraction near the horizon actually compresses the disk slightly in the vertical direction rather than magnifying it.
This mismatch between measurement and perception is called the Moon illusion.
Visual context changes apparent scale
There is no single explanation accepted as complete, but distance cues and size comparison are central. Near the horizon, the Moon appears among familiar objects and within a landscape our visual system interprets as distant. High in the sky, it floats in an empty field with few scale references.
You can test the effect by photographing the Moon with a fixed focal length at moonrise and later in the night. Overlay the disks and they will be nearly the same size. You can also view the horizon Moon through a narrow tube or between your fingers to remove surrounding context; it often seems less gigantic.
Use the illusion creatively
Although it is perceptual, the experience is real. A long lens can place the Moon behind a distant landmark, making both appear large in the frame. That is optical perspective and composition, not atmospheric enlargement. Accurate moonrise azimuth and elevation help position the camera far enough from the foreground to create the intended alignment.
