Given on a clear sunny day, the only light that is blocking the star light is the scattered blue light of atmosphere.

If we make use of a notch filter, which blocks only the blue light, can we get to see the stars? Will the sky turn black and give us a feel as if there is no atmosphere?!

Or is the atmospheric scattering spread across a wider spectrum that a filter to block the scattering light ends up blocking most of star light too?!

  • 4
    $\begingroup$ Considering that the sky is typically pale blue rather than a deep blue, I expect that all visible wavelengths are present and quite bright. Biased towards the shorter wavelengths but not restricted to them. $\endgroup$
    – badjohn
    Nov 24, 2018 at 9:05
  • 2
    $\begingroup$ Worth reading? $\endgroup$
    – Farcher
    Nov 24, 2018 at 11:25
  • $\begingroup$ see this skysurfer.eu/daystars.php $\endgroup$
    – anna v
    Nov 24, 2018 at 12:15
  • 1
    $\begingroup$ A polarizing filter might also help. $\endgroup$
    – user4552
    Nov 24, 2018 at 15:41
  • $\begingroup$ @BenCrowell so, a filter and a polariser it is! The hunt begins for the duo! $\endgroup$ Nov 24, 2018 at 18:14

1 Answer 1


Here is the range of blue cone reception in frequncies, and then it is the biology of color perception that takes over:

The graphic below is a sensitivity curve that depicts the range of wavelengths and the sensitivity level for the three kinds of cones.

enter image description here


The filter you propose seems to cover (430-500nm)

That leaves a lot of blue sensitive perception free, so I would guess no, it would not work.

Here is the content that gives the blue of the sky in frequencies :

blue sky

A spectrum taken of blue sky clearly shows solar Fraunhofer lines and the atmospheric water absorption band.

Nevertheless, if you have access to such a filter ,why don't you try, on a clear day? or put it on a camera and take a picture in daytime?

  • $\begingroup$ I wish to! If I get hands on some filter, I will! What will be the spectrum of the scattering from the atmosphere? Is it as continuous as sun’s? $\endgroup$ Nov 24, 2018 at 12:53
  • $\begingroup$ see my edit above $\endgroup$
    – anna v
    Nov 24, 2018 at 13:00
  • 1
    $\begingroup$ The spectrum of blue sky peaks well below 500nm. The spectrum you show appears to be the spectrum of sunlight. $\endgroup$
    – ProfRob
    Mar 8 at 8:54

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