What Causes the Colorful Cross in Photos of Sirius?

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Discussion Overview

The discussion revolves around the colorful cross observed in a photograph of Sirius, which was created by placing two strings in front of the camera lens. Participants explore the reasons behind the rainbow-like colors of the cross, considering various optical phenomena.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that the colorful effect resembles white light interference fringes and suggests that diffraction at the corners of the strings may produce subsidiary images that interfere with each other.
  • Another participant agrees that the colors are likely due to interference fringes and mentions that using different filters can enhance the effect, referencing an example image.
  • A question is raised about the orientation of the cross of light in relation to the strings, specifically whether it would align with the strings or be rotated if interference is indeed the cause.

Areas of Agreement / Disagreement

Participants generally agree that the colorful cross is likely related to interference phenomena, but there is uncertainty regarding the specific mechanics and orientation of the effect.

Contextual Notes

There are unresolved questions about the exact nature of the optical effects involved, including the dependence on specific conditions such as the use of filters and the alignment of the strings.

pixel01
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My friend took this picture of Sirius. He put 2 strings as a cross in front of the lens and there is the cross in the pic. But we do not know why there's the color of the cross, it resembles the color of a rainbow.
 

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What a wonderful effect.To me it bears a closer resemblance to white light interference fringes.Perhaps subsidiary images are produced by diffraction at the four corners where the two strings cross and the light from these then interferes.This is only a guess and I would like to hear what other people think.
 
This may be a silly question, but would the cross of light line up with the cross of the strings, or would it be rotated by 45 degrees if interference is the cause?
 

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