Astrophotography w/ Digital SLR Sensor Sensitivity

Discussion in 'Digital Photography' started by Billy, Jan 25, 2009.

  1. Billy

    Billy Guest

    I recently began taking images of stars from my Nikon D300 digial SLR
    and I'm amazed - when I take the picture I can many more stars in the
    image than I can with the naked eye. Does anyone know why this would
    happen, could the image sensor be stronger than my eyesight?????
     
    Billy, Jan 25, 2009
    #1
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  2. Billy

    Marvin Guest

    The sensors in a digicam integrate the light that is
    received over the length of an exposure. Your eye-brain
    sensor isn't as good about integration.

    The eye has a large dynamic intensity range in part because
    it changes the lens opening and has other mechanisms for
    adjusting sensitivity over time. Are your eyes fully
    dark-adapted when you look up at the sky?
     
    Marvin, Jan 25, 2009
    #2
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  3. Billy

    Don Stauffer Guest

    Unfortunately, you cannot "adjust" the exposure time with the human eye.
    It turns out the quantum efficiency of the two are pretty comparable,
    but you can make a long exposure with the camera, so it is collecting
    more photons than the eye.
     
    Don Stauffer, Jan 25, 2009
    #3
  4. Billy

    Billy Guest

    amazing, didnt know this!
     
    Billy, Jan 25, 2009
    #4
  5. Billy

    Pat Guest

    I didn't know you collected photons. I have some -- including some
    rare ones -- that I was thinking about selling. I boxed up some
    lovely purple ones in 1972, if you are interesting. Plus I have the
    complete set of Kennedy Commemorative ones.
     
    Pat, Jan 25, 2009
    #5
  6. Billy

    Jeff R. Guest

    This isn't just a "digital" thing - exactly the same thing happens
    (fortunately!) with film.

    I have only ever seen (visually - not photographically) the Coal Sack nebula
    a couple of times - these when I've been way out bush with carefully
    dark-adapted eyes - yet I have managed to photograph it (film) from my
    heavily light-polluted Sydney suburban backyard.

    It takes exposures of only a couple of seconds to make naked-eye-invisible
    stars appear on film.

    One of the reasons I enjoy astrophotography so much.

    Hint: in order to increase your astro fun, google: "barn door mounts"
     
    Jeff R., Jan 25, 2009
    #6
  7. Billy

    Ray Fischer Guest

    You can't set your eyes to take a 30-second exposure.

    And, as a related bit of trivia: one of the longest exposures ever
    taken is the 1,000,000 second Hubble deep-field photo.

    http://hubblesite.org/newscenter/archive/releases/2004/07/
     
    Ray Fischer, Jan 26, 2009
    #7
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