When was the concept of dark eye adaption for telescopic observations invented?

Answer 1

Hi. I don't think anyone 'invented' it. Your eyes become more sensitive to low levels of light quite naturally. Maybe you mean 'averted vision'. This uses a part of your retina that is even more sensitive by looking off to the side of the dim object you are observing. I do not know who first discovered this. http://www.answers.com/main/ntquery?s=averted+vision&gwp=13

Answer 2

It's probably been known since the dawn of the species that your eyes adapt to darkness gradually after a light source is taken away. As people have always looked at the sky, and have observed it intently since ancient civilisation, I suppose that they've always taken advantage of that fact.

It's only in the last fifty years or less that light pollution has become an issue and we've had to think about "dark adaptation" seriously. Up to the late 1800s, many large observatories were built in major cities for obvious reasons. There's one in the middle of Paris. It's now used for solar observing because of the light, but it obviously was not a problem even in the city back then.