3 ms·

not to rain on the parade here but reading the date on a dime puts you well into sub-milliarcsecond territory, well past what is possible to resolve with even a

not to rain on the parade here but reading the date on a dime puts you well into sub-milliarcsecond territory, well past what is possible to resolve with even a diffraction limited optical light telescope of any kind from space. Bigger telescope systems can resolve smaller objects, but even if you were to yeet an enormous, optically perfect, 10m telescope into the very lowest earth orbit possible (not maintainable due to atmospheric drag) you would still be a couple orders of magnitude away from being able to read the date on a dime.

burnte 6y ago
I believe his intent, especially with the word "purportedly", was so infer that the proposed system had amazing abilities, less than it was intended to be a perfectly accurate description.
- 0_____0 6y ago
  I agree that it wasn't intended to be literal fact, just figured I'd take the opportunity to flex my mediocre optical systems knowledge. :p
  - jerzmacow 6y ago
    Could you describe what size of optical telescope you'd need to put in space to read the date on a dime? I'm very curious
    - 0_____0 6y ago
      Check out this chart. https://en.wikipedia.org/wiki/Diffraction-limited_system#/media/File:Diffraction_limit_diameter_vs_angular_resolution.svg https://en.wikipedia.org/wiki/Diffraction-limited_system#/me... I would guess that you'd need 0.25mm resolution, which at 200km would require 250microarcseconds angular res, which doesn't even register on that graph at any wavelength or size of telescope lol edit: this is a very 'spherical cow' analysis. i'm pretty sure that atmospheric effects will kill your ability to image stuff like this well before angular resolution will.
      - aasasd 6y ago
        That chart is beautiful. While not really Tufte's dream of ‘a ton of measurements in little ink’, that chart shows me everything I'd want to know about this one relation. Also, perhaps there's a need for a better naming system than one that produces ‘Extremely Large Telescope’.
        0_____0 6y ago
        It's a bit of a joke as well, hence: https://en.m.wikipedia.org/wiki/Overwhelmingly_Large_Telescope https://en.m.wikipedia.org/wiki/Overwhelmingly_Large_Telesco...
  - titzer 6y ago
    Impressive! I was going to comment going on gut feeling from layman's understanding of resolving power of optics, but glad to see someone who knows more nail it.
bb123 6y ago
What does"sub-milliarcsecond territory" mean? I know nothing of satellite tech.
- 0_____0 6y ago
  it's an angular measurement. applied here it means the angular resolution of an optical system. a degree of arc is divided into minutes of arc (MoA)(1/60 degree each), and there are 60 arcseconds in a minute of arc. Two points that are 1 milliarcsecond apart, projected on a flat surface 200km away, are about 1mm apart on that surface. edit: (can plug "tan(0.001 arcseconds) * 200km in mm" into google to check this out for yourself)
KirillPanov 6y ago
> even if you were to yeet an enormous, optically perfect, 10m telescope 10m is a tiny aperture: https://en.m.wikipedia.org/wiki/Synthetic-aperture_radar https://en.m.wikipedia.org/wiki/Synthetic-aperture_radar

burnte 6y ago

I believe his intent, especially with the word "purportedly", was so infer that the proposed system had amazing abilities, less than it was intended to be a perfectly accurate description.

0_____0 6y ago
I agree that it wasn't intended to be literal fact, just figured I'd take the opportunity to flex my mediocre optical systems knowledge. :p
- jerzmacow 6y ago
  Could you describe what size of optical telescope you'd need to put in space to read the date on a dime? I'm very curious
  - 0_____0 6y ago
    Check out this chart. https://en.wikipedia.org/wiki/Diffraction-limited_system#/media/File:Diffraction_limit_diameter_vs_angular_resolution.svg https://en.wikipedia.org/wiki/Diffraction-limited_system#/me... I would guess that you'd need 0.25mm resolution, which at 200km would require 250microarcseconds angular res, which doesn't even register on that graph at any wavelength or size of telescope lol edit: this is a very 'spherical cow' analysis. i'm pretty sure that atmospheric effects will kill your ability to image stuff like this well before angular resolution will.
    - aasasd 6y ago
      That chart is beautiful. While not really Tufte's dream of ‘a ton of measurements in little ink’, that chart shows me everything I'd want to know about this one relation. Also, perhaps there's a need for a better naming system than one that produces ‘Extremely Large Telescope’.
      - 0_____0 6y ago
        It's a bit of a joke as well, hence: https://en.m.wikipedia.org/wiki/Overwhelmingly_Large_Telescope https://en.m.wikipedia.org/wiki/Overwhelmingly_Large_Telesco...
- titzer 6y ago
  Impressive! I was going to comment going on gut feeling from layman's understanding of resolving power of optics, but glad to see someone who knows more nail it.

bb123 6y ago

What does"sub-milliarcsecond territory" mean? I know nothing of satellite tech.

0_____0 6y ago
it's an angular measurement. applied here it means the angular resolution of an optical system. a degree of arc is divided into minutes of arc (MoA)(1/60 degree each), and there are 60 arcseconds in a minute of arc. Two points that are 1 milliarcsecond apart, projected on a flat surface 200km away, are about 1mm apart on that surface. edit: (can plug "tan(0.001 arcseconds) * 200km in mm" into google to check this out for yourself)

KirillPanov 6y ago

> even if you were to yeet an enormous, optically perfect, 10m telescope 10m is a tiny aperture: https://en.m.wikipedia.org/wiki/Synthetic-aperture_radar https://en.m.wikipedia.org/wiki/Synthetic-aperture_radar