Armed with sensitive cameras and radio telescopes, Mr. Ashcraft hunts for sprites — majestic emanations of light that flash for an instant high above the thunderheads, appearing in the shapes of red glowing jellyfish, carrots, angels, broccoli, or mandrake roots with blue dangly tendrils. (Weather buffs call the tall, skinny ones “diet sprites.”) No two are alike.
And they are huge — tens of miles wide and 30 miles from top to bottom. But because they appear and vanish in a split-second, the naked eye tends to perceive them only as momentary flashes of light. It takes a high-speed camera to capture them in detail.
Depending on his skill and luck and the presence of storms, Mr. Ashcraft might get one or two sprite images a night, or more than 300. From June through August this year, he captured sprite images on 29 nights.
One of a growing corps of citizens who advance the scientific process in every field from astronomy to zoology, he sends his best images to Steven A. Cummer, a professor of electrical and computer engineering at Duke University who leads a multicenter project called Phocal, for Physical Origins of Coupling to the Upper Atmosphere by Lightning.
“We happily take images captured by anyone, either our own cameras or those of citizen scientists like Thomas Ashcraft,” Dr. Cummer said. A goal is to capture sprite images from multiple locations to triangulate their position relative to the lightning that creates them.