Colin Humphreys and W. G. Waddington of Oxford University considered the possibility that a lunar, rather than solar, eclipse might have taken place. They concluded that such an eclipse would have been visible, for thirty minutes, from Jerusalem and suggested the gospel reference to a solar eclipse was the result of a scribe wrongly amending a text. Historian David Henige dismisses this explanation as 'indefensible' and astronomer Bradley Schaefer points out that the lunar eclipse would not have been visible during daylight hours.
What does Colin Humphreys dismiss the explanation as?