Space artist Ron Miller has created a series of images that illustrate the sizes of the other planets in our solar system in a way that makes them a bit more accessible, showing what they would look like if they were 240,000 miles away -- the approximate distance of the moon from the Earth. He began with a picture of the moon over Death Valley (up top), and then calculated the number of degrees in the sky a given planet would take up at that distance. "For instance," he explained to me over email, "the moon covers just 1/2 a degree. Venus would cover about two degrees, so it would appear about four time larger than the moon."
The other thing Miller decides is how wide to make the entire picture. "I usually choose 50 or 60 degrees, which emulates a typical snapshot," he explains. "This determines how much space the planet takes up in the final picture."