This is a photo I have taken with a microscope (100x objective). What are these circles? When I rotate the eyepiece or the objective they stay still. Are they particles on the mirror? In this case what kind of particles?

What are these circles?

  • $\begingroup$ Can you make them sharper by changing the focus? $\endgroup$ – BowlOfRed Jun 10 '16 at 20:32
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    $\begingroup$ looks like dust. $\endgroup$ – philip_0008 Jun 10 '16 at 20:34
  • $\begingroup$ Funny, that's how I've always imagined a photon in my head, but those are surely not photons. $\endgroup$ – M Barbosa Jun 10 '16 at 20:37
  • $\begingroup$ They stay the same regardless of focus. I just realized that because they don't move when the eyepiece is turned (the camera) this means that they are attached to it. So it may be as @philip_0008 suggested just dust particles on the camera lenses. $\endgroup$ – Aalex Gabi Jun 10 '16 at 20:40
  • $\begingroup$ After cleaning the camera few of them are left. Does this have any connection with airy disks? $\endgroup$ – Aalex Gabi Jun 10 '16 at 20:50

As suggested in comments these circles are airy disks around dust particles on the camera lens. After wiping the lens few of them were left and the remaining ones moved.

You can find out more about airy disks on Wikipedia

  • 5
    $\begingroup$ You gave yourself the correct answer. It's caused by Airy disks around dust particles. $\endgroup$ – CuriousOne Jun 10 '16 at 20:58
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    $\begingroup$ Good evidence for it being due to interference is the fact that the inside of the first ring is blue and the outside is red. $\endgroup$ – Farcher Jun 11 '16 at 13:34

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