Why stack ????

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denababy
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Why stack ????

Post by denababy »

Hi, I was at an outreach event at the Space center in Leicester at the weekend and whilst having a conversation with someone, they asked ‘why stack pics of the Sun?’ I tried to answer but found my answer a little light on detail. Anyone got any answers so I can pinch them and use them in the future?


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Merlin66
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Re: Why stack ????

Post by Merlin66 »

Start with fast frame imaging capturing those moments of best seeing...
Stacking these “best” frames gives a better signal to noise image and improved quality when processed.


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Re: Why stack ????

Post by marktownley »

Stacking takes a lot of images and gets the sharpest bits from all of them combining to make a single image that is sharper than any of the many taken in the original avi file.


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pedro
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Re: Why stack ????

Post by pedro »

It's all about getting the best S/N ratio and reducing noise


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MalVeauX
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Re: Why stack ????

Post by MalVeauX »

As others pointed out, the summary of it all is to reduce apparent (random) noise which increases the signal to noise ratio. The signal to noise ratio increases by the square root of the number of images in the stack, but there are limits before artifacts or additional blur issues come in. So why do this? Because differentiating actual signal (detail, structure, objects, etc) from noise makes a big difference when resolving something so that you're recording the subject and not just noise. The increase in dynamic range due to lack of noise allows more latitude in processing too so that you can manipulate the data without simply manipulating the noise, such as sharpening the noise, or stretching the histogram full of noise, as you're just processing noise at that point. But if the noise is removed, you have more latitude to process before re-introducing noise. A lot of the simple processes we use with solar processing really rely on the image to have a high signal to noise ratio, so very low to no noise, and high dynamic range, to allow for the best processing. Deconvolution and unsharp masks for example really require this.

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