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meteoptic-l [ät] ursa.fi
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Lew, in re your query about deep-sky telescopic viewing, the effect
you're talking about happens at very low light levels. The physiology of
the eye is such that different sizes of things are optimally detected at
different brightness levels. In brightly-illuminated scenes, low contrast
things can be detected even if fairly small, while at low levels they need
to be big (about 1-3 degrees apparent size is about optimum for deep-sky
observing).
\Brian
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