Safety first! Using a proper solar filter is important. Solar filters block the powerful radiation from the Sun and must be in perfect condition before any use. Dr Chou is an optometrist who has studied the effects of solar observing on the human eye (his articles appear online). And a phoropter is that strange device eye doctors use to test what prescription you might need. Combining that with solar observing is just silly of course.

(c) Eclipse Nuts Cartoon by Bill Kramer. Uploaded Tue, 28 Mar 17 08:11:08 -0400