But technically, the moon is always a constant distance from the earth. The theory suggests that we use depth and distance cues from the surrounding environment to judge perceived distances to the moon. However, a moon overhead is only surrounded by stars and empty space, which provide no reliable or recognizable distance cues that can be used to gauge the distance to the moon. Therefore, we may think that the moon overhead is closer than the one on the horizon. How the moon is perceived as it moves across the sky.
Viewers perceive that the moon overhead is closer than the moon at the horizon.
Thus if two images are the same size on the retina, but one is perceived as farther away, the image with the greater apparent distance is perceived as larger in size. In the figure the two yellow horizontal lines are actually the same lengths. However, the top line is perceived as longer since the sense of perspective makes the top line seem farther away from the viewer. Thus there are two lines of the same length, but one seems farther away. This farther line looks longer.