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by woko 2152 days ago
From your link:

> The way this process works is that, while averaging all of the pixels in a series of, say, 10 images, the program mathematically calculates which pixels fall far away from the mean value because they're much brighter (or much fainter) compared to the same pixels in other frames. The algorithm then discards those out-of-range pixel values so they don’t affect the final image.

Wouldn't this process remove part of the comet trails as well as the satellite trails?

I mean, I get how it works if all you care about is relatively static like distant stars, but would it work for this specific use case?
3 comments
spacemark 2152 days ago
The most common algorithm to manage airplanes, satellites, hot pixels, and other undesired photons in astrophotos is a process called Kappa-Sigma Clipping. It essentially rejects pixel values from subframes in your image stack that fall outside a user-inputted deviation from the mean.

In other words, the process works wonderfully to get rid of the starlink-emitted photons, but you lose that subframe's signal, lowering your signal to noise ratio. Not the end of the world. But inconvenient and sometimes costly to professional astronomers.

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CydeWeys 2152 days ago
Yeah, but what % of subframes (small portions of large images) are ruined by noise caused by moving objects? Way less than 1% I'd imagine. It's just not a big problem. And certainly not worth outlawing new satellite launches over.
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Sharlin 2152 days ago
No, because the comet does not perceptibly move in the sky during the acquisition. All comet pixels are present in every image.
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_Microft 2152 days ago
The comet does not change but its position in the sky does btw. Longer exposure times turn points into streaks if the object is not tracked to compensate for this.
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Sharlin 2152 days ago
Yes, I assumed tracking as it's basically a mandatory requirement when you do telephoto astrophotography, and definitely used in the OP photo. The alternative is to shoot wider angle and align the images during stacking, but either way you have to get your subject's pixels aligned or the result is just blur.
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CydeWeys 2152 days ago
This is true of every single object in the night sky, and is why an equatorial tracking mount is table stakes for good astrophotography.
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sixothree 2152 days ago
Take a look at this

https://photoshoptrainingchannel.com/remove-tourists-stack-m...

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