4 ms·

I'm curious how the starless versions are created. From the steps at the end, I couldn't see a 'this is how stars are removed' step. Maybe it's part of stacking

I'm curious how the starless versions are created. From the steps at the end, I couldn't see a 'this is how stars are removed' step. Maybe it's part of stacking (but most stars would remain present?) or the calibration process treating stars as noise?

roblh 7mo ago
I feel like the stars are probably pretty easy to mask out since they’re very bright relative to the rest of the image. Once you have the mask, each one is small enough that you could probably fill it with the values from adjacent pixels. Kinda like sensor mapping to hide dead pixels. That’s just a guess though, I’m sure there’s more to it than that.
- touisteur 7mo ago
  Bright stars are so bright they literally mask areas of the sky. You'll probably need deconvolution algorithms (CLEAN being the standard some time ago, don't know whether some AI/deep-inv approach works nowadays...) to remove them.
  - joshumax 7mo ago
    There are several “AI” deconvolution tools to remove stars which work exceptionally well: two of the most popular ones being StarNet and RC-Astro’s StarXTerminator. I’m willing to bet that the author used the latter for star removal as it’s become something of a standard in the astrophotography world.
inaros 7mo ago
>> I'm curious how the starless versions are created. Its done with using dedicated astrophotography software (StarXTerminator). Example: https://astrobackyard.com/starnet-astrophotography/ https://astrobackyard.com/starnet-astrophotography/ So these are more artistic photo works than real science photos... Rod Prazeres the Astrophotographer, has given this interview where he talks about the process: https://www.astronomy.com/observing/the-astrophotography-of-project-hail-mary/ https://www.astronomy.com/observing/the-astrophotography-of-...
- teraflop 7mo ago
  So this part of the blog post is essentially false: "no generative AI of any kind" I have yet to see a precise technical definition of what "generative AI" means, but StarXTerminator uses a neural network that generates new data to fill in the gaps where non-stellar objects are obscured by stars. And it advertises itself as "AI powered".
  - cj 7mo ago
    I don't consider photos I take on iPhone to be "AI generated" or even "AI augmented" even though iPhone uses neural networks and "AI" to do basic stuff like low light photography, blurring backgrounds, etc.
    - teraflop 7mo ago
      I agree that I wouldn't call these photos "AI generated", because the majority of what you're seeing is real. But that's very different to saying that no generative AI was used at all in their production. "AI augmented" sounds pretty accurate to me. Likewise, if someone posted a photo taken with their iPhone where they had used the built-in AI features to (for instance) remove people or objects, and then they claimed that no AI was involved, I would consider that misleading, even if the photo accurately depicts a real scene in other respects.
    - hatthew 7mo ago
      As a photographer and machine learning guy, I would call a lot of modern phone photos AI augmented. AI to stack photos or figure out what counts as the background is a little bit of a gray area, but an img-to-img CNN is about as close as you can get to full AI generation without a full GAN or diffusion model.
  - inaros 7mo ago
    So funny people are downvoting you... https://astrobackyard.com/starnet-astrophotography/ https://astrobackyard.com/starnet-astrophotography/ “StarNet is a neural network that can remove stars from images in one simple step leaving only the background. More technically, it is a convolutional residual net with encoder-decoder architecture and with L1, Adversarial and Perceptual losses.”
knappe 7mo ago
Traditionally (pre-ai) you would use another image of the same part of the sky and negate the items that you want to remove from the image As an example terrestrial telescope mirrors get dusty. You're not going to break down the scope just to clean up the dust as this is a many days operation in most cases. So instead you would take "flats" that were of a pure white background and thus showed the dust in its full, dusty, glory. When you take your actual images, you negate (subtract from the original image) the flat and thus any noise generated by the dust. You can use this same method for removing brighter stars from an image that would otherwise saturate the ccd and wash out the background. Turns out it doesn't work for planes. Ask me how I know!
- dotancohen 7mo ago
  > Traditionally (pre-ai) you would use another image of the same part of the sky and negate the items that you want to remove from the image. I'm not an astrophotographer, so I'm interested about why that method would work for stars. Are not stars fixed in relation to the images taken? I could see how the technique would work with planets, maybe, but not stars. Why does the technique not work with aircraft? Because they generally fly on fixed routes?
  - recursivegirth 7mo ago
    Earth moves - that's how you get the next shot without repositioning the telescope. This time-lapse probably better visualizes it: https://www.youtube.com/watch?v=wFpeM3fxJoQ https://www.youtube.com/watch?v=wFpeM3fxJoQ
    - dotancohen 7mo ago
      As the Earth rotates over the course of the night, the background stars and nebulae move as a single unit, no? Maybe for some close stars parallax might work to remove them over the course of half a year. But no way could the Earth's rotation during a single night move background stars out of a nebulae.
    - hatthew 7mo ago

roblh 7mo ago

I feel like the stars are probably pretty easy to mask out since they’re very bright relative to the rest of the image. Once you have the mask, each one is small enough that you could probably fill it with the values from adjacent pixels. Kinda like sensor mapping to hide dead pixels. That’s just a guess though, I’m sure there’s more to it than that.

touisteur 7mo ago
Bright stars are so bright they literally mask areas of the sky. You'll probably need deconvolution algorithms (CLEAN being the standard some time ago, don't know whether some AI/deep-inv approach works nowadays...) to remove them.
- joshumax 7mo ago
  There are several “AI” deconvolution tools to remove stars which work exceptionally well: two of the most popular ones being StarNet and RC-Astro’s StarXTerminator. I’m willing to bet that the author used the latter for star removal as it’s become something of a standard in the astrophotography world.

inaros 7mo ago

>> I'm curious how the starless versions are created. Its done with using dedicated astrophotography software (StarXTerminator). Example: https://astrobackyard.com/starnet-astrophotography/ https://astrobackyard.com/starnet-astrophotography/ So these are more artistic photo works than real science photos... Rod Prazeres the Astrophotographer, has given this interview where he talks about the process: https://www.astronomy.com/observing/the-astrophotography-of-project-hail-mary/ https://www.astronomy.com/observing/the-astrophotography-of-...

teraflop 7mo ago
So this part of the blog post is essentially false: "no generative AI of any kind" I have yet to see a precise technical definition of what "generative AI" means, but StarXTerminator uses a neural network that generates new data to fill in the gaps where non-stellar objects are obscured by stars. And it advertises itself as "AI powered".
- cj 7mo ago
  I don't consider photos I take on iPhone to be "AI generated" or even "AI augmented" even though iPhone uses neural networks and "AI" to do basic stuff like low light photography, blurring backgrounds, etc.
  - teraflop 7mo ago
    I agree that I wouldn't call these photos "AI generated", because the majority of what you're seeing is real. But that's very different to saying that no generative AI was used at all in their production. "AI augmented" sounds pretty accurate to me. Likewise, if someone posted a photo taken with their iPhone where they had used the built-in AI features to (for instance) remove people or objects, and then they claimed that no AI was involved, I would consider that misleading, even if the photo accurately depicts a real scene in other respects.
  - hatthew 7mo ago
    As a photographer and machine learning guy, I would call a lot of modern phone photos AI augmented. AI to stack photos or figure out what counts as the background is a little bit of a gray area, but an img-to-img CNN is about as close as you can get to full AI generation without a full GAN or diffusion model.
- inaros 7mo ago
  So funny people are downvoting you... https://astrobackyard.com/starnet-astrophotography/ https://astrobackyard.com/starnet-astrophotography/ “StarNet is a neural network that can remove stars from images in one simple step leaving only the background. More technically, it is a convolutional residual net with encoder-decoder architecture and with L1, Adversarial and Perceptual losses.”

knappe 7mo ago

Traditionally (pre-ai) you would use another image of the same part of the sky and negate the items that you want to remove from the image As an example terrestrial telescope mirrors get dusty. You're not going to break down the scope just to clean up the dust as this is a many days operation in most cases. So instead you would take "flats" that were of a pure white background and thus showed the dust in its full, dusty, glory. When you take your actual images, you negate (subtract from the original image) the flat and thus any noise generated by the dust. You can use this same method for removing brighter stars from an image that would otherwise saturate the ccd and wash out the background. Turns out it doesn't work for planes. Ask me how I know!

dotancohen 7mo ago
> Traditionally (pre-ai) you would use another image of the same part of the sky and negate the items that you want to remove from the image. I'm not an astrophotographer, so I'm interested about why that method would work for stars. Are not stars fixed in relation to the images taken? I could see how the technique would work with planets, maybe, but not stars. Why does the technique not work with aircraft? Because they generally fly on fixed routes?
- recursivegirth 7mo ago
  Earth moves - that's how you get the next shot without repositioning the telescope. This time-lapse probably better visualizes it: https://www.youtube.com/watch?v=wFpeM3fxJoQ https://www.youtube.com/watch?v=wFpeM3fxJoQ
  - dotancohen 7mo ago
    As the Earth rotates over the course of the night, the background stars and nebulae move as a single unit, no? Maybe for some close stars parallax might work to remove them over the course of half a year. But no way could the Earth's rotation during a single night move background stars out of a nebulae.
  - hatthew 7mo ago