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Astronomy and Cosmology
Astronomy and Astrophysics
Diffraction Effects and Artifacts in Telescopes like the JWST
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[QUOTE="collinsmark, post: 6815915, member: 114325"] [USER=199289]@sophiecentaur[/USER], Who's not reading what other people have written? Could you clarify that? Do you even read what [I]you[/I] write?! Sure. Right here. [USER=683547]@Devin-M[/USER] was kind enough to generate one with direct experiment. Those two stars are of [I]different[/I] brightness (as acquired directly from the camera). But when adjusting for the intensity, it's quite clear that the diffraction patterns are of the same size. [ATTACH type="full" alt="60a8c309-ca23-46a9-9f9a-051e4c3f1f85-jpeg.jpg"]316364[/ATTACH] ------ Edit: My objection was your statement where you said the spikes were not "detect[I]able[/I]" (italics mine). I don't have an objection to saying that they were not detect[I]ed[/I] in a particular image. But they are in fact detect[I]able[/I]. --------- I [I]never [/I]said JWST does not use stacking. I kindly request that you do not put words in my mouth. I've never said that in my life. Not on PF, not anywhere. That said, I'd be tickled to know where you think I said that. Which post and where. Show me a quote, if you would be so kind. No it doesn't. It essentially says, among other things, that the standard deviation of a set of averaged trials decreases by a factor approaching [itex] \frac{1}{\sqrt{N}} [/itex] compared to the standard deviation of the original set of trials. It says absolutely nothing about saturating sensors. The input is [I]already[/I] quantized. From the very beginning. It starts with individual, quantized photons. From there all merely count them. We sum them. Sometimes we divide the results by a number. Nothing about any of that is nonlinear. We can put those numbers in a 16 bit register or a 32 bit register. We can store those numbers in a file using 16 bit format or 32 bit floating point format. It doesn't matter. Saturation is nonlinear, but that doesn't happen when stacking. That is one of the primary motivations to use stacking in the first place: it avoids saturation and nonlinearity. Stacking is about as linear as linear can get. What do you think stacking is? Averaging (as in "mean" -- [I]not[/I] median) pixels from different subframes is what stacking [I]is[/I]. The addition operator is a very linear operator. Division (by the number of elements summed) is a linear operator. What's not linear about that?! Where does the math fail? Show me, please. How might you suggest informing astronomers that use JWST, Hubble (HST), and pretty much any telescope around the world, that their stacking algorithms -- algorithms that they've been using for [I]decades[/I] -- are all failures? Do you propose invalidating the countless academic papers that relied on astronomical data that invariably was produced, in part, using same general mathematical principles and theorems discussed here? [/QUOTE]
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Diffraction Effects and Artifacts in Telescopes like the JWST
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