With all due respect, deepiron, that is not true. There is no lensing effect that makes them bigger. As measured, they simply do not appreciably increase or decrease in size at the horizon. Any "lensing" would none the less be measurable... caliper the moon or sun, and compare to zenith. This is entirely psychological. It is because when the sun or moon is at the horizon you can compare it to the objects also on the horizon. In the case of the sun, you can actually look right at it, which in itself is an issue since you really cannot dwell on the size at zenith.
The refraction that does occur bends the path of the light such that the sun/moon appear above the horizon longer, and the setting is actually a couple minutes after they are under the horizon. It doesn't grossly change the geometry. At low altitudes in particular, you can see some distortion, but the size is largely unchanged (perhaps measurable, but were talking arc seconds here, not, "wow, that's HUGE!"). The distortion is actually a flattening in the vertical due to the atmosphere acting as a prism. So in one dimension it is actually smaller, not larger.
ATR, that image looks big because it's taken with a telephoto lens (or cropped), no more.
The sun and moon are not bigger at the horizon, period.
In fact, they are farther away at sun/moon rise or set by one earth radius.
tater
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