Q+A CENTER

Clarification: A story in the July/August issue (Using the Earth's Atmosphere for High-Performance Night Vision) drew the attention of reader Robert Eather of KEO Consultants in Brookline, Mass.

In the story about the NoblePeak Vision's germanium-enhanced CMOS sensors, author Stephen Germino described "night glow" as "being created by the interaction of the earth's atmosphere with the solar winds. It starts with the solar winds agitating hydrogen and oxygen ions 90 km high in the earth's atmosphere, causing these ions to release their energy in the form of light."

Mr. Eather made two points: It has nothing to do with the solar wind, and there are no hydrogen ions at 90 km. "The nightglow [more commonly called airglow]," he wrote, "is caused by recombination of photoionized oxygen and nitrogen ions [ionized by solar UV during daytime] and chemiluminescence from oxygen and nitrogen reacting with hydroxyl ions."

Phil Davies, VP Sales and Marketing at NoblePeak (Wakefield, Mass.), said, "I think the confusion is down to the use of solar wind vs. solar radiation, two very different things, wind being particles and radiation the electromagnetic spectrum where UV plays a big role in night glow generation. However, we never said hydrogen, but have always said hydroxyl OH in all of our literature. Please accept our apologies."