Could it really be that huge?
It’s all a matter of perspective. :)
The moon is over 2000 miles across; it only looks small because of the distance. Because it’s so far away, moving around on earth doesn’t really change its apparent size. But as you walk away from a building, it looks a lot smaller a lot faster. Line them up at the right distance (this fellow was about 15 miles away from the observatory) with a lens long enough that the moon fills the frame, this is the result.
The apparent size is caused by refraction. Back when I was a navigator (before GPS) we had published tables to correct for the distortion when using the moon for a celestial fix.