Skywatchers without solar eclipse glasses can still safely observe Wednesday's eclipse by building a pinhole projector from household materials, according to the National Aeronautics and Space Administration. A total solar eclipse crossed the Arctic, Greenland, Iceland, northern Spain and a small part of Portugal on Aug. 12, marking the first total eclipse visible from mainland Europe since 1999. Direct viewing of any phase of a partial eclipse without protection can cause permanent eye damage, NASA said. Eclipse glasses meeting the ISO 12312-2 international safety standard remain the recommended method for direct viewing, but supplies can run low near major eclipse events. This matters because the eclipse drew large crowds to viewing sites across Iceland and Spain, and demand for eclipse glasses can outstrip supply close to the event.