1. Cape Town
    Joined
    14 Apr '05
    Moves
    52945
    04 Oct '11 06:57
    Originally posted by googlefudge
    With an unbelievably long exposure time ;-)
    Presumably sensor sensitivity is limited by the number of photons actually arriving ie it doesn't matter how sensitive your sensor if there are no photons to detect.
    So, given perfect sensitivity, what exposure time would be required to image a planets surface at the nearest star for a given total mirror size?

    If the planet rotates at the same speed as the earth, then the exposure cant be more than a few minutes or the motion blur would be too great, although I guess we could get round that with various tricks.

    Does motion blur already give us problems when trying to image planets in our own solar system, or are the exposure times nice and short?
  2. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    53223
    15 Oct '11 13:07
    Originally posted by twhitehead
    Presumably sensor sensitivity is limited by the number of photons actually arriving ie it doesn't matter how sensitive your sensor if there are no photons to detect.
    So, given perfect sensitivity, what exposure time would be required to image a planets surface at the nearest star for a given total mirror size?

    If the planet rotates at the same speed ...[text shortened]... when trying to image planets in our own solar system, or are the exposure times nice and short?
    Motion blur definitely reduces resolution compared to the same probe sitting still over a subject. The motion of a planet around its star could probably be compensated for by digitally adding the images together like we do now for faint objects. If the controlling computer can collate the photons to a single source it would get around the movement of the planet. Obviously the more mirrors and the bigger the mirrors the better but present propulsion technology and size of launch vehicles will limit the size of the mirrors. I think the James Webb scope, it it ever gets launched, now in doubt, has mirrors that pop into place when it gets to its observing site, I think at one of the L1 lagrangians, one of them a few million miles from earth. Although it is still a single telescope not using aperture synthesis.
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