Stars twinkle because of the atmosphere's slightly fluctuating refractive properties (compare to mirages). I'm sure you can notice dim stars disappearing when you look straight at them, but I'm going to keep the atmosphere story for now - even though the only way I've tested it is to compare with planets (whose images are disclike rather than pointlike).
Comment author:rmmh
04 July 2011 03:00:36PM
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I take it you haven't spent much time star gazing?
The "foveal blind spot" is how the fovea has a very high density of cones, which gives great acuity with color vision, but unfortunately almost no rods, so very poor performance under low-light conditions.
To view faint stars, you look slightly off to the side while still concentrating on the object. This is called averted vision.
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Stars twinkle because of the atmosphere's slightly fluctuating refractive properties (compare to mirages). I'm sure you can notice dim stars disappearing when you look straight at them, but I'm going to keep the atmosphere story for now - even though the only way I've tested it is to compare with planets (whose images are disclike rather than pointlike).
See any number of google hits on "why stars twinkle" e.g. http://astroprofspage.com/archives/1168
I take it you haven't spent much time star gazing?
The "foveal blind spot" is how the fovea has a very high density of cones, which gives great acuity with color vision, but unfortunately almost no rods, so very poor performance under low-light conditions.
To view faint stars, you look slightly off to the side while still concentrating on the object. This is called averted vision.