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It's trivial to erase these things from photos. The photographer no doubt knows this, but that isn't the point. It's perfectly reasonable for scientists to wan

It's trivial to erase these things from photos. The photographer no doubt knows this, but that isn't the point. It's perfectly reasonable for scientists to want to capture accurate data on the space surrounding the main subject being imaged. Simply erasing the satellites from photos does not recover the data on the space behind. Any data from behind the satellites is lost forever. This photo keeps the satellites in order to visually demonstrate this problem. Remember that astronomy today is often done on a single pixel of data. Starlink blocks multiple pixels, and even ruins entire exposures when they flare up. This will make astronomical research, like searching for exoplanets, far harder and more expensive than it is today. Space telescopes are, and will always be, orders of magnitude more expensive than ground telescopes to launch, maintain and operate.

claydavisss 6y ago
Starlink will provide an immediate benefit to humanity, the astronomy performed otherwise, won't. Looking for exoplanets isn't a practical concern for humanity any time soon.
- ganafagol 6y ago
  Odd perspective when defending technology from the same guy that wants to save humankind by literally colonizing other objects in space.
  - zdragnar 6y ago
    Not necessarily- exoplanets beyond our solar system really aren't going to be feasible to physically travel to until we can come up with something along the lines of faster-than-light travel. Given the lack of light pollution on Mars, I almost wonder if we wouldn't be better off doing all of our astrophysical study out there or in deep space anyway (assuming we have a steady supply of transit back and forth to transfer the data since streaming isn't likely to have good enough quality for a long time either). Then again, I am also not a fan of putting more satellites into orbit either... mostly just struck by your comment as being not terribly odd to me.
    - ClumsyPilot 6y ago
      Ofcourse astrophysical study works better in soace, but who is oaying the added cost of launching telescioes to space? Travelling to exoplanets is not hard, it just takes 1000 - 10,000 years. There will be no FTL untill we can manipulate black holes, if ever at all. So the first trip to exoplanels will be in a multi-hundred year hybernation, or a genration ship, or people that are so different from us that they don't mind the journey.
nsilvestri 6y ago
Exposures are generally taken frequently enough that any that would be problematic for data can simply be dropped. The satellites aren't permanently positioned in the sky. Geostationary satellites permanently lose any data behind them (although I haven't heard of a geostationary satellite being positioned precisely problematically).
- irthomasthomas 6y ago
  Searching for exoplanets moving in front of a star, involves measuring the luminosity of a single pixel for ~1% change. Dropping frames ruined by a satellite train isn't going to work. E.g https://www.sciencealert.com/a-bunch-of-potential-tabby-s-star-alikes-have-just-been-identified https://www.sciencealert.com/a-bunch-of-potential-tabby-s-st...
  - nsilvestri 6y ago
    You absolutely can drop those frames. Exoplanetary transits are generally in the range of 1 to 4 hours, and hundreds of exposures may be taken in that time. In my undergraduate I studied astronomy and some of my classmates did an exoplanet detection project with a 61" scope and had issues with satellites on a handful of frames. Sure, it sucks to lose 2 minutes worth of data, but it's not even lose to catastrophic when you have the data before and after as well.
  - CamperBob2 6y ago
    Absolute bunk. As numerous people have tried to explain in this thread (along with its frequent predecessors), anything that moves across frames is by definition unimportant when stacking images. It's literally the difference between integration and differentiation. Satellites move fast. Not only that, but you know exactly where and when they will cross your field of view, and for how long they'll remain within it. If the astronomy community can't muster the rudimentary image processing technology needed to reject satellites and other transient objects, I'm not exactly confident in their ability to finally figure out the whole origin-of-the-Universe thing.
    - 6y ago
giantrobot 6y ago
For one a Starlink satellite, or any LEO satellite, is moving really fast relative to a ground based telescope. It'll occult any given star for a fraction of a second. If you're doing a narrow field long exposure with tracking, that will be problematic and you'll loose data. Most scientific observations don't do long exposures, especially measuring highly variable things like exoplanet transits. It's more effective to stack a large number of short exposures for scientific measurements. It's much easier to eliminate noise because everything that is not noise will be transient for a single frame in the stack. You can also remove frames with things like satellites, clouds, or airplanes without losing much data. Knowing the ephemeris of satellites also allows observations to time short exposures to avoid occultations. Astronomers have been dealing with satellites, clouds, and airplanes for a long time. Amateur astronomers might have a harder time with Starlink satellites but they will adapt just like they did with the ISS and Iridium.
- irthomasthomas 6y ago
  "Members of the LSST science team said last month that, assuming the full deployment of SpaceX’s Starlink satellites, nearly every exposure from the observatory within two hours of sunset or sunrise would have a satellite streak. During summer months, when twilight times longer, there could be a 40 percent impact on twilight observing time, according to the Association of Universities for Research in Astronomy, or AURA, which manages the LSST project for the National Science Foundation. “Because of scattered light in the optics by the bright satellites, the scientific usefulness of an entire exposure can sometimes be negated,” AURA said in a statement last month. “Detection of near-Earth asteroids, normally surveyed for during twilight, would be particularly impacted. Dark energy surveys are also sensitive to the satellites because of streaks caused in the images. Avoiding saturation of streaks is vital.”" https://spaceflightnow.com/2019/12/09/spacex-to-experiment-with-less-reflective-satellite-coatings-on-next-starlink-launch/ https://spaceflightnow.com/2019/12/09/spacex-to-experiment-w...
  - LeifCarrotson 6y ago
    They're trying to do a logical OR for all the light that comes in during a long exposure, as in an old film camera with a long shutter time. That may have worked with analog film before we had satellites, but Starlink is just the latest and brightest addition to the sky that makes that an increasingly bad idea. Change is hard, but it's not that difficult. Instead, AND a bunch of shorter exposures. Then, your streaks are not streaks, but a series of point sources that can be removed trivially.
mlindner 6y ago
This is completely incorrect. The data is not lost, when you stack images the low signal of a single (or multiple) satellites in a single image disappears into the noise.
- serf 6y ago
  > The data is not lost point me to the data behind the occlusion on a single frame.
dzhiurgis 6y ago
There’s no sats up north...
kbenson 6y ago
If the images are stacked, doesn't that mean that there's plenty of images with the parts that are occluded in others not occluded? I understand for any specific image, there's going to be some lost background because of Starlink satellites, but that's not what this is showing, this is showing something that's not possible, right? Shifting all the satellites temporally so they appear together, arbitrarily maximizing the problem beyond what is real isn't an accurate depiction of the problem, IMO. Put another way, if you erase the Starlink satellites from the images before stacking them, you then get a fairly accurate representation of the sky without any Starlink satellites, and you still have the data behind them (from the other pictures where that portion of the sky was not occluded). You can also probably fix the intensity of anything occluded in a few of the pictures but not others through some math.
- cma 6y ago
  > If the images are stacked, doesn't that mean that there's plenty of images with the parts that are occluded in others not occluded? As he mentioned, flare can cover a broader area of the sensor.
  - kbenson 6y ago
    There's still many other images that the flare isn't affecting that area at all though, right? The point is that there's many different images used here, and instead of combining them in a way to remove transient artifacts, which is the norm, they combined them in a way to emphasize transient artifacts, which is not something people normally would want to do. It's worse than any single image that's used to make it, so why make it at all?
    - Rusky 6y ago
      It's an interesting way to demonstrate the density of the satellites- they're not hiding the number or duration of images, so you can get a fuzzy intuition for how likely you are to catch them in a given image.
      - 6y ago
deleted 6y ago
[deleted]

claydavisss 6y ago

Starlink will provide an immediate benefit to humanity, the astronomy performed otherwise, won't. Looking for exoplanets isn't a practical concern for humanity any time soon.

ganafagol 6y ago
Odd perspective when defending technology from the same guy that wants to save humankind by literally colonizing other objects in space.
- zdragnar 6y ago
  Not necessarily- exoplanets beyond our solar system really aren't going to be feasible to physically travel to until we can come up with something along the lines of faster-than-light travel. Given the lack of light pollution on Mars, I almost wonder if we wouldn't be better off doing all of our astrophysical study out there or in deep space anyway (assuming we have a steady supply of transit back and forth to transfer the data since streaming isn't likely to have good enough quality for a long time either). Then again, I am also not a fan of putting more satellites into orbit either... mostly just struck by your comment as being not terribly odd to me.
  - ClumsyPilot 6y ago
    Ofcourse astrophysical study works better in soace, but who is oaying the added cost of launching telescioes to space? Travelling to exoplanets is not hard, it just takes 1000 - 10,000 years. There will be no FTL untill we can manipulate black holes, if ever at all. So the first trip to exoplanels will be in a multi-hundred year hybernation, or a genration ship, or people that are so different from us that they don't mind the journey.

nsilvestri 6y ago

Exposures are generally taken frequently enough that any that would be problematic for data can simply be dropped. The satellites aren't permanently positioned in the sky. Geostationary satellites permanently lose any data behind them (although I haven't heard of a geostationary satellite being positioned precisely problematically).

irthomasthomas 6y ago
Searching for exoplanets moving in front of a star, involves measuring the luminosity of a single pixel for ~1% change. Dropping frames ruined by a satellite train isn't going to work. E.g https://www.sciencealert.com/a-bunch-of-potential-tabby-s-star-alikes-have-just-been-identified https://www.sciencealert.com/a-bunch-of-potential-tabby-s-st...
- nsilvestri 6y ago
  You absolutely can drop those frames. Exoplanetary transits are generally in the range of 1 to 4 hours, and hundreds of exposures may be taken in that time. In my undergraduate I studied astronomy and some of my classmates did an exoplanet detection project with a 61" scope and had issues with satellites on a handful of frames. Sure, it sucks to lose 2 minutes worth of data, but it's not even lose to catastrophic when you have the data before and after as well.
- CamperBob2 6y ago
  Absolute bunk. As numerous people have tried to explain in this thread (along with its frequent predecessors), anything that moves across frames is by definition unimportant when stacking images. It's literally the difference between integration and differentiation. Satellites move fast. Not only that, but you know exactly where and when they will cross your field of view, and for how long they'll remain within it. If the astronomy community can't muster the rudimentary image processing technology needed to reject satellites and other transient objects, I'm not exactly confident in their ability to finally figure out the whole origin-of-the-Universe thing.
  - 6y ago

giantrobot 6y ago

For one a Starlink satellite, or any LEO satellite, is moving really fast relative to a ground based telescope. It'll occult any given star for a fraction of a second. If you're doing a narrow field long exposure with tracking, that will be problematic and you'll loose data. Most scientific observations don't do long exposures, especially measuring highly variable things like exoplanet transits. It's more effective to stack a large number of short exposures for scientific measurements. It's much easier to eliminate noise because everything that is not noise will be transient for a single frame in the stack. You can also remove frames with things like satellites, clouds, or airplanes without losing much data. Knowing the ephemeris of satellites also allows observations to time short exposures to avoid occultations. Astronomers have been dealing with satellites, clouds, and airplanes for a long time. Amateur astronomers might have a harder time with Starlink satellites but they will adapt just like they did with the ISS and Iridium.

irthomasthomas 6y ago
"Members of the LSST science team said last month that, assuming the full deployment of SpaceX’s Starlink satellites, nearly every exposure from the observatory within two hours of sunset or sunrise would have a satellite streak. During summer months, when twilight times longer, there could be a 40 percent impact on twilight observing time, according to the Association of Universities for Research in Astronomy, or AURA, which manages the LSST project for the National Science Foundation. “Because of scattered light in the optics by the bright satellites, the scientific usefulness of an entire exposure can sometimes be negated,” AURA said in a statement last month. “Detection of near-Earth asteroids, normally surveyed for during twilight, would be particularly impacted. Dark energy surveys are also sensitive to the satellites because of streaks caused in the images. Avoiding saturation of streaks is vital.”" https://spaceflightnow.com/2019/12/09/spacex-to-experiment-with-less-reflective-satellite-coatings-on-next-starlink-launch/ https://spaceflightnow.com/2019/12/09/spacex-to-experiment-w...
- LeifCarrotson 6y ago
  They're trying to do a logical OR for all the light that comes in during a long exposure, as in an old film camera with a long shutter time. That may have worked with analog film before we had satellites, but Starlink is just the latest and brightest addition to the sky that makes that an increasingly bad idea. Change is hard, but it's not that difficult. Instead, AND a bunch of shorter exposures. Then, your streaks are not streaks, but a series of point sources that can be removed trivially.

mlindner 6y ago

This is completely incorrect. The data is not lost, when you stack images the low signal of a single (or multiple) satellites in a single image disappears into the noise.

serf 6y ago
> The data is not lost point me to the data behind the occlusion on a single frame.

dzhiurgis 6y ago

There’s no sats up north...

kbenson 6y ago

If the images are stacked, doesn't that mean that there's plenty of images with the parts that are occluded in others not occluded? I understand for any specific image, there's going to be some lost background because of Starlink satellites, but that's not what this is showing, this is showing something that's not possible, right? Shifting all the satellites temporally so they appear together, arbitrarily maximizing the problem beyond what is real isn't an accurate depiction of the problem, IMO. Put another way, if you erase the Starlink satellites from the images before stacking them, you then get a fairly accurate representation of the sky without any Starlink satellites, and you still have the data behind them (from the other pictures where that portion of the sky was not occluded). You can also probably fix the intensity of anything occluded in a few of the pictures but not others through some math.

cma 6y ago
> If the images are stacked, doesn't that mean that there's plenty of images with the parts that are occluded in others not occluded? As he mentioned, flare can cover a broader area of the sensor.
- kbenson 6y ago
  There's still many other images that the flare isn't affecting that area at all though, right? The point is that there's many different images used here, and instead of combining them in a way to remove transient artifacts, which is the norm, they combined them in a way to emphasize transient artifacts, which is not something people normally would want to do. It's worse than any single image that's used to make it, so why make it at all?
  - Rusky 6y ago
    It's an interesting way to demonstrate the density of the satellites- they're not hiding the number or duration of images, so you can get a fuzzy intuition for how likely you are to catch them in a given image.
    - 6y ago

deleted 6y ago

[deleted]