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57395Re: Dizzying Panoramas Of Stars In Motion

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  • Erik Krause
    Jul 29, 2014
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      Am 29.07.2014 18:12, schrieb Keith Martin:
      > Second, judging by the shot at the start that shows a large metal '+'
      > with the cameras mounted at the end of each arm, the cameras are much
      > further offset than they need to be. Moving them as close together as
      > possible would make the output more reliable.

      You could even use a one shot solution. A circular fisheye pointed
      straight up covers the whole sky, which would be perfect for long
      exposures. And since those comet-like star trails are more or less
      artificial anyway (normal star trails don't fade), one could think about
      completely artificial trails.

      As Helmut Dersch showed years ago
      <http://www.panotools.org/dersch/startrail/trail.html> star trails are
      straight and equally long in an equirectangular projection with the
      zenith at polaris. So it should be easy to create "star trails" by a
      simple motion blur of a sky panorama. (In fact it's not so easy, since
      the trails darken due to blur. You need to duplicate layer with mode
      lighten, shift 1px and flatten). This would reduce shooting to start and
      end of the night in order to also cover stars that rise during the night.

      Furthermore stars are colored. This is seldom visible, since stars show
      as points which are overexposed very quickly while other stars are not
      even visible. If you defocus slightly, stars are more like disks, which
      don't overexpose that fast. Could be light pollution prohibits this - I
      discovered it on altiplano in Peru 4000m above sea level and hundreds of
      miles away from any city, one of the darkest regions on earth.

      Erik Krause
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