Talk:Arago spot

message: Man, I did this experiment back in college. We used a penny and taped it to a couple of strands of hair. After a bit of tinkering with the laser, the spot showed up quite clearly. I'll ask my old professor if they still do that and if they can get a photo of it. --W0lfie (talk) 17:44, 27 October 2008 (UTC)

message: Why is this article titled "Arago spot" rather than its usual name? Cesiumfrog (talk) 01:37, 11 April 2009 (UTC)
thread_title:  Poisson's spot 

message: At the bottom, please note "mulitples" for "multiples". That's an easy mistake to make.
I don't yet know how to submit a corrected image, unfortunately.
Regards, Nikevich (talk) 01:56, 21 July 2011 (UTC)
thread_title:  The diagram <Poissonspotintensity.jpg> has a typo 

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thread_title:  External links modified (January 2018) 

message: What are g and b in the integrals?
ElizabethGreene (talk) 17:47, 23 April 2018 (UTC)
replies: text: They are distances (g=P_0C and b=CP_1) in the diagram above the integrals (it would be better if they were marked on the diagram however, not just in the text...). L3erdnik (talk) 00:11, 24 April 2018 (UTC)
thread_title:  Math Questions 

message: Although there are a number of secondary claims of prior observation, I can vouch that the linked paper by Delisle contains no mention of the Arago spot. It speaks only of the rings surrounding a circular shadow. Here is a translation of the pertinent part (the remainder is a discussion of prior observations of eclipses and the experimental setup):
The reference should be replaced by a correct one or the claim should be rescinded. -- Xerxes (talk) 15:14, 9 January 2019 (UTC)
thread_title:  Claims Concerning Observation of the Spot Prior to Arago 

message: The basic requirements described (lower bound of Fresnel number and smoothness of the occluder) imply that one can observe Arago's spot arbitrarily close to the occluder. However, the numerical simulation diagram shows it absent for some distance behind the occluder (roughly for F > 10).
I think that either:
* there's something missing in the basic requirements, or
* the numerical simulation simulated a non-point source, which should then be mentioned (along with source's size) in the description of the diagram.
81.6.39.156 (talk) 10:53, 5 December 2021 (UTC)
thread_title:  Basic requirements appear not to be sufficient 

message: I am a graduate physicist and have designed, built, owned, repaired, and used Newtonian telescopes for well over half a century now. So to me, this statement appears very wrong:
In astronomy, the Arago spot can also be observed in the strongly defocussed image of a star in a Newtonian telescope. There, the star provides an almost ideal point source at infinity, and the secondary mirror of the telescope constitutes the circular obstacle.
If you "strongly defocus" a Newtonian, you get a blurred image of the shadow / silhouette of the secondary, yes. And indeed, the edges of the mirror and the secondary holder are very heavily diffracted. BUT that image is nowhere near the size of the quoted Fresnel number. In something like even an f/11 teelscope, you are not going to get anywhere near the amount of diffracted light "bending" around the mirror to make a visible spot. So I dispute that statement. 2001:8003:E490:7D01:C00:4BC3:111:7AE7 (talk) 00:29, 1 September 2023 (UTC)
thread_title:  Questionable statement about "in astronomy"