For some ambitious photographers, the summer thunderstorm season means one thing: capturing spites.
These electrical discharges, which occur high over thunderstorm clouds, can be as elusive to catch as their name implies. But not this summer.
“Lately there has been a bumper crop of sprites,” amateur astronomer and long-time sprite hunter Thomas Ashcraft said in an interview with SpaceWeather.com.
Ashcraft this week photographed a particularly massive sprite over western Oklahoma, nearly 300 miles away from his observatory in New Mexico.
“According to my measurements, it was 40 miles tall and 46 miles wide. This sprite would dwarf Mt. Everest,” Ashcraft told SpaceWeather.com
Sprites have been observed for at least 100 years, but hard evidence of their existence didn’t come until 1989 when they were imaged by cameras flying aboard a NASA space shuttle, according to astronomer Tony Phillips, who runs the SpaceWeather.com website.
“My method for photographing sprites is fairly simple,” Ashcraft told Phillips. “First I check for strong thunderstorms within 500 miles using regional radar maps accessible on the Internet. There must be a locally clear sky to image above the distant storm clouds.
“Then I aim my cameras out over the direction of the thunderstorms — which will be hot red or purple on the radar maps — and shoot continuous DSLR exposures. I usually shoot continuous 2-second exposures but if there is no moon then I will shoot up to 4-second exposures. Then I run through all the photographs and if I am lucky some sprites will be there. It might take hundreds to usually thousands of exposures, so be prepared for many shutter clicks.”
Ashcraft does his sprite hunting with a modified near-infrared DLSR but any DLSR will work, he added. “It does require persistence and a little bit of luck.”
Photo: Near-infrared image of triple sprites over Oklahoma on June 23. Credit: Thomas Ashcraft for Discovery News