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Because they choose not to take photos of the surrounding stars, and those that are visible they either photoshop out or process the images in such a way that t

by avar 7y ago

Because they choose not to take photos of the surrounding stars, and those that are visible they either photoshop out or process the images in such a way that they're not visible. There's a sibling comment saying it's due to the exposure, that's wrong. That's not how Hubble works, it's not just a giant digital camera in orbit. The "photo" you're looking at is a composite from tens or hundreds of other images, so to start with most of the pixels you're looking at are just black filler. You can see the black and white raw images at http://hst.esac.esa.int/ehst/#home http://hst.esac.esa.int/ehst/#home search for "SATURN" under "Solar System Objects" and sort by date. A lot of the Hubble images from June 20th, 2019 have stars, including some visible between the rings and Saturn. They were just edited out because showing them wasn't the point.

michelb 7y ago
Is there a good explanation/article about how they take/process these images? I would have liked it if they could have included a bit of text about why certain items were not in the picture/removed.
biot 7y ago
Are those stars? The “iduy37thq” image [0], for example, has various star-like points of light on top of the planet itself in addition to appearing in the background. [0] http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=iduy37thq_flt.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R...
- Ididntdothis 7y ago
  This look like the noise I get from my camera when I take very long exposures (> 10 minutes). The sensor starts heating up and producing these dots.
- xioxox 7y ago
  No they're probably not (I'm an astronomer). They're likely cosmic rays. When I've used Hubble data, then the processing uses multiple images to remove the cosmic rays (which aren't in common between images).
  - metafunctor 7y ago
    I'd love to understand how those bright dots and lines (so, cosmic rays?) appear on these images.
    - xioxox 7y ago
      They're just high energy particles that interact with the CCD cameras typically used for astronomy. You get a bright point or particle track, as the particle interacts with the CCD producing electrons. This is worse for space telescopes, as there are more cosmic rays in space. For some simple information see: http://spiff.rit.edu/classes/phys373/lectures/cosmic_rays/cosmic_rays.html http://spiff.rit.edu/classes/phys373/lectures/cosmic_rays/co...
xioxox 7y ago
I'm an astronomer, and I think you're probably wrong. It's mostly down to exposure. Those little dots you're seeing in the images are likely cosmic rays. Those are removed by combining multiple images, as cosmic rays don't appear in the same places.
- avar 7y ago
  The pixel-sized dots are cosmic rays, those are obviously artifacts as some of them can be seen in front of Saturn. I'm referring to objects you can consistently see between different observations. E.g. this one around 1/2 a planet width from the pole you can't see observed from 2018-06-06 14:35:05 until 2018-06-06 14:46:35: http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o2q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o3q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o4q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o5q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... Although looking again perhaps that's a moon of Saturn's rather than a particularly bright star. Not an astronomer, just an interested amateur. The few times I've been curious enough to look at the raw data behind these images I've found background celestial objects that are definitely edited out. That's understandable, the point is to show e.g. Saturn and not whatever background objects happened to be there at the time Hubble took the photo. I'm just pointing out it's not all due to the light exposure.

by avar 7y ago

michelb 7y ago

Is there a good explanation/article about how they take/process these images? I would have liked it if they could have included a bit of text about why certain items were not in the picture/removed.

biot 7y ago

Are those stars? The “iduy37thq” image [0], for example, has various star-like points of light on top of the planet itself in addition to appearing in the background. [0] http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=iduy37thq_flt.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R...

Ididntdothis 7y ago
This look like the noise I get from my camera when I take very long exposures (> 10 minutes). The sensor starts heating up and producing these dots.
xioxox 7y ago
No they're probably not (I'm an astronomer). They're likely cosmic rays. When I've used Hubble data, then the processing uses multiple images to remove the cosmic rays (which aren't in common between images).
- metafunctor 7y ago
  I'd love to understand how those bright dots and lines (so, cosmic rays?) appear on these images.
  - xioxox 7y ago
    They're just high energy particles that interact with the CCD cameras typically used for astronomy. You get a bright point or particle track, as the particle interacts with the CCD producing electrons. This is worse for space telescopes, as there are more cosmic rays in space. For some simple information see: http://spiff.rit.edu/classes/phys373/lectures/cosmic_rays/cosmic_rays.html http://spiff.rit.edu/classes/phys373/lectures/cosmic_rays/co...

xioxox 7y ago

I'm an astronomer, and I think you're probably wrong. It's mostly down to exposure. Those little dots you're seeing in the images are likely cosmic rays. Those are removed by combining multiple images, as cosmic rays don't appear in the same places.

avar 7y ago
The pixel-sized dots are cosmic rays, those are obviously artifacts as some of them can be seen in front of Saturn. I'm referring to objects you can consistently see between different observations. E.g. this one around 1/2 a planet width from the pole you can't see observed from 2018-06-06 14:35:05 until 2018-06-06 14:46:35: http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o2q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o3q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o4q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?RETRIEVAL_TYPE=PRODUCT&ARTIFACT_ID=idg236o5q_raw.jpg http://hst.esac.esa.int/ehst-sl-server/servlet/data-action?R... Although looking again perhaps that's a moon of Saturn's rather than a particularly bright star. Not an astronomer, just an interested amateur. The few times I've been curious enough to look at the raw data behind these images I've found background celestial objects that are definitely edited out. That's understandable, the point is to show e.g. Saturn and not whatever background objects happened to be there at the time Hubble took the photo. I'm just pointing out it's not all due to the light exposure.