3 ms·

I'm no expert either, but I imagine that high exposure times come with more motion blur. So just cranking up exposure time does not necessarily result in better

I'm no expert either, but I imagine that high exposure times come with more motion blur. So just cranking up exposure time does not necessarily result in better pictures.

IshKebab 4y ago
Motion of what?
- dontlistentome 4y ago
  everything everywhere all at once
- spookthesunset 4y ago
  Minor changes to the satellite position? Vibration from some hardware? I dunno but the parent asks a question I ask too. When you do long exposure, any kind of movement, even very small, can degrade your image. How JWST handles movement during long exposure is a good question. Same with hubble.
  - adgjlsfhk1 4y ago
    long exposure images aren't actually 1 continuous exposure. you take a ton of individual images and composite them using known reference points.
- ryneandal 4y ago
  Well I mean the JWST is in orbit both around the L2 point and the sun. It's sensitive equipment must also be facing away from the sun. So there's a lot of movement going on out there.
dylan604 4y ago
I'm sorry but no no no. These telescopes are tracking the objects they are imaging specifically to avoid imaging issues from motion. This isn't some dude in the backyard with an alt-az scope bought from a Sears catalog. I really hope you were trolling with this response
ryneandal 4y ago
Here's out exposure time works for JWST: https://jwst-docs.stsci.edu/understanding-exposure-times https://jwst-docs.stsci.edu/understanding-exposure-times
dredmorbius 4y ago
There's effectively no motion blur visible. The most pronounced effects might be paralax of nearby stars to thousands of light-years at the outside. That would be observable in images taken at opposite sides of Earth's orbit around the Sun, a baseline of about 300 million km (186 million miles). Even that will be phenomenally small, too small to be observable for most objects within our own galaxy (the Milky Way) let alone the distant objects JWST is most concerned with. From Wikipedia: In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions of nearby stars, increasing the number of stellar parallaxes measured to milliarcsecond accuracy a thousandfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy. The Hubble telescope WFC3 now has a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 3,066 parsecs (10,000 ly) for a small number of stars.[10] This gives more accuracy to the cosmic distance ladder and improves the knowledge of distances in the Universe, based on the dimensions of the Earth's orbit. https://en.wikipedia.org/wiki/Stellar_parallax https://en.wikipedia.org/wiki/Stellar_parallax JWST's optical acuity is roughly similar to Hubble --- despite the larger mirror surface, it's using longer wavelengths of electromagnetic radiation, with lower resolving power. Movement of the JWST itself is kept to an absolute minimum for obvious reasons. It would simply be unusable as a telescope if this weren't the case. Absolute motion of objects being imaged ... also isn't a factor, as the maximum resoultion of JWST (the smallest pixels on an image) are still tremendous. It's possible that a nearbye (neighbouring galaxy) nova event might generate observable motion over days or weeks, but even that is unlikely. The interesting stuff in that event is actually the changes in brightness and evolution of light emissions, for the most part. In the case of the Carina Nebula image 8,500 light years distant (that is, astronomically near), the individual dust segments are light years in length. The distance from the Earth to the Sun is roughly 1/64,000th that distance --- too small to visualise in thos images. The individual stars show are not dots or disks, but points, whose apparent size is a matter of refraction and saturation effects on the JWST itself. Even where there migh be any movement, individual images are composed of multiple exposures and "stacked" to take median observed signal strengths. This is, in a way, to eliminate motion effects, but the moving entities are cosmic rays which create random signatures on the sensors of JWST, and not movement of the telescope or its targets themselves.

I'm no expert either, but I imagine that high exposure times come with more motion blur. So just cranking up exposure time does not necessarily result in better pictures.

IshKebab 4y ago

Motion of what?

dontlistentome 4y ago
everything everywhere all at once
spookthesunset 4y ago
Minor changes to the satellite position? Vibration from some hardware? I dunno but the parent asks a question I ask too. When you do long exposure, any kind of movement, even very small, can degrade your image. How JWST handles movement during long exposure is a good question. Same with hubble.
- adgjlsfhk1 4y ago
  long exposure images aren't actually 1 continuous exposure. you take a ton of individual images and composite them using known reference points.
ryneandal 4y ago
Well I mean the JWST is in orbit both around the L2 point and the sun. It's sensitive equipment must also be facing away from the sun. So there's a lot of movement going on out there.

dylan604 4y ago

I'm sorry but no no no. These telescopes are tracking the objects they are imaging specifically to avoid imaging issues from motion. This isn't some dude in the backyard with an alt-az scope bought from a Sears catalog. I really hope you were trolling with this response

ryneandal 4y ago

Here's out exposure time works for JWST: https://jwst-docs.stsci.edu/understanding-exposure-times https://jwst-docs.stsci.edu/understanding-exposure-times

dredmorbius 4y ago

There's effectively no motion blur visible. The most pronounced effects might be paralax of nearby stars to thousands of light-years at the outside. That would be observable in images taken at opposite sides of Earth's orbit around the Sun, a baseline of about 300 million km (186 million miles). Even that will be phenomenally small, too small to be observable for most objects within our own galaxy (the Milky Way) let alone the distant objects JWST is most concerned with. From Wikipedia: In 1989 the satellite Hipparcos was launched primarily for obtaining parallaxes and proper motions of nearby stars, increasing the number of stellar parallaxes measured to milliarcsecond accuracy a thousandfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy. The Hubble telescope WFC3 now has a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 3,066 parsecs (10,000 ly) for a small number of stars.[10] This gives more accuracy to the cosmic distance ladder and improves the knowledge of distances in the Universe, based on the dimensions of the Earth's orbit. https://en.wikipedia.org/wiki/Stellar_parallax https://en.wikipedia.org/wiki/Stellar_parallax JWST's optical acuity is roughly similar to Hubble --- despite the larger mirror surface, it's using longer wavelengths of electromagnetic radiation, with lower resolving power. Movement of the JWST itself is kept to an absolute minimum for obvious reasons. It would simply be unusable as a telescope if this weren't the case. Absolute motion of objects being imaged ... also isn't a factor, as the maximum resoultion of JWST (the smallest pixels on an image) are still tremendous. It's possible that a nearbye (neighbouring galaxy) nova event might generate observable motion over days or weeks, but even that is unlikely. The interesting stuff in that event is actually the changes in brightness and evolution of light emissions, for the most part. In the case of the Carina Nebula image 8,500 light years distant (that is, astronomically near), the individual dust segments are light years in length. The distance from the Earth to the Sun is roughly 1/64,000th that distance --- too small to visualise in thos images. The individual stars show are not dots or disks, but points, whose apparent size is a matter of refraction and saturation effects on the JWST itself. Even where there migh be any movement, individual images are composed of multiple exposures and "stacked" to take median observed signal strengths. This is, in a way, to eliminate motion effects, but the moving entities are cosmic rays which create random signatures on the sensors of JWST, and not movement of the telescope or its targets themselves.