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Smallest difference in magnitude detectable by human eye?

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I'm trying to figure out some stuff related to how human vision works and this question is important part of the puzzle.

Let's take average human and a telescope of some aperture (pretty sharp, low magnification - stars are still point like and airy disk is not resolved), two stars of very close magnitude. What needs to be magnitude difference between two stars (same spectral class, so color is the same, everything is the same except brightness) for most people to say - yes I can see that one is brighter (very slightly so) than the other?

Does it vary with brightness? Maybe at mag 5 we can spot 0.2 mag difference while at mag 10 we can spot only 0.4 mag difference?

How does aperture of telescope affect this (I'm guessing it will affect this if visible mag difference depends on brightness of stars)?

Either personal experience or "general knowledge" are welcome answers.

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Posted (edited)

Hi Vlaiv

In the psychophysics literature these things are known as JNDs (just-noticeable differences) so if you search for this term you are bound to come across some relevant scientific studies. A good astronomy-related resource is chapter 2 of Roger Clark's book Visual Astronomy of the Deep Sky. (The relevant pages appear to be accessible on Google books).





Edited by Martin Meredith
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