The advice was prepared by the Particle Physics and Astronomy Research Council "in consultation with the ... Department of Health". But a spokeswoman said it contradicts warnings this week by the Chief Medical Officer, Liam Donaldson, who said the only safe way to view the eclipse is to turn your back on it or watch it on television.
A code drawn up by the research council emphasises the importance of never looking at the Sun directly, because infrared radiation can painlessly burn the retina and so cause permanent eye damage or blindness. Unlike the Department of Health, the research council endorses special filters, provided they carry the "CE" mark of the British Standards Institution. The council's also says that, providing people are in the zone of totality, where the Sun is entirely eclipsed by the Moon, it is safe to look directly at the total eclipse with the naked eye. "Only then is it safe to view the totally eclipsed Sun directly without any filter ...
"But do be alert to the reappearance of the Sun's brilliant disc at the end of the total phase. As soon as the first light of the Sun has reappeared, producing a spectacular 'diamond ring', you must look away immediately and use the special filter once more."
Professor Donaldson said that such behaviour is dangerous and he advises people to make a pinhole projector to view the eclipse indirectly by facing away from the Sun.
But Ralph Chou, associate professor of Optometry at the University of Waterloo in Ontario and an international adviser on eye safety, accused Professor Donaldson of ignoring scientific evidence.
The main causes of eye damage during eclipses are the result of viewing the partly eclipsed Sun without eye protection, looking through the pinhole of an indirect projector and viewing the Sun through inadequate viewing filters, such as sunglasses, he said.
"Messages that discourage an activity or behaviour, particularly when they are intended for young people, can backfire. This is especially so when the warnings turn out to be inaccurate or wrong."