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  1. #1
    BetterSense's Avatar
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    44-exposure analemma

    http://arxiv.org/pdf/1106.3141v1

    On page 9 of this horologically interesting article, you can see a 44-exposure analemma. Now, I didn't know what an analemma is until I saw this, so let me explain that it's a multiple-exposure photo of the sun, which forms a figure-8 pattern in the sky.

    This is interesting and I would like more information about the photographer and how the photograph was made. I assume that the pictures of the sun (the dots) were taken at a radically reduced exposure, so that the sky area received almost no exposure at all so that it came out correctly when the final 'correct' exposure was made. I wonder how this was achieved for the solstice trails, though. It seems the shutter must be left open for those. Would you use slide film or negative film? Does anyone have any more information on this fascinating photograph or how one might go about duplicating it in thought or in reality?
    f/22 and be there.

  2. #2
    holmburgers's Avatar
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    Wow, that is really cool.

    If you take an average daytime reading of the foreground, and then underexpose that by a factor of 44, or slightly less, the sun should probably still make an image on the film, but only after 43 more exposures will the foreground be exposed to a normal level.

    But like you say,,, no idea how the solstice trails were captured.
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  3. #3
    polyglot's Avatar
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    The sun is so much stupidly brighter than the background that all you need is lots and lots of ND, perhaps in the form of a Baader solar filter foil. With such a foil on, you could expose all afternoon and have only the sun register on the image, hence the streaks.

    Edit: the filter-factor on solar foil is about 100,000, which is over 16 stops.
    Last edited by polyglot; 06-28-2011 at 06:59 PM. Click to view previous post history.

  4. #4
    hpulley's Avatar
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    Quote Originally Posted by polyglot View Post
    The sun is so much stupidly brighter than the background that all you need is lots and lots of ND, perhaps in the form of a Baader solar filter foil. With such a foil on, you could expose all afternoon and have only the sun register on the image, hence the streaks.

    Edit: the filter-factor on solar foil is about 100,000, which is over 16 stops.
    Baader film was invented in 1999 or so. In 1978, mylar was your best bet though for photographic use only, smoked glass could be used (dangerous by eye due to UV). Glass filters came later, then Baader film. Many used welder's glass visually and the dangerous SUN filters sold with cheap telescopes.

    You can get photographic Baader film (3) which isn't nearly as many stops so you can use shorter exposures than the visual stuff. You could use multiple layers of Baader film to really bring it down.

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  5. #5
    tomalophicon's Avatar
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    Not really on-topic, and most have seen, but check out this picture which is a 6 month exposure of London.

  6. #6
    spacer's Avatar
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    According to the text, he exposed the foreground separately, when the sun was out of the frame.

  7. #7
    BetterSense's Avatar
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    I got that part, but it still seems like the sky would over-expose when exposing the streaks, which must have been several hour exposures.
    f/22 and be there.

  8. #8
    Lee L's Avatar
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    Quote Originally Posted by BetterSense View Post
    http://arxiv.org/pdf/1106.3141v1
    Now, I didn't know what an analemma is until I saw this, so let me explain that it's a multiple-exposure photo of the sun, which forms a figure-8 pattern in the sky.
    Not really accurate, probably due to poor grammar. An analemma isn't a multiple exposure photo, it's the pattern made by the sun when solar observations (not necessarily photographs) are made at a certain standardized clock time each day, and reflects the combined effects of the earth's changing speed in its slightly elliptical orbit, and the tilt of the earth's spin axis relative to the plane of its orbit around the sun. Analemma drawings are very common on sundials and on globes.

    The photo in your post is by Dennis DiCicco, who was the first known to photograph it in this way. See: http://www.twanight.org/newTWAN/photos.asp?ID=3001422

    There are a number of analemma photos by one prolific and well-known photographer at:
    http://www.perseus.gr/Astro-Solar-Analemma.htm along with the data on how he made his exposures.

    Lee

  9. #9
    spacer's Avatar
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    I just bought a house in the country, and have a Nikon FM10 that probably won't get used much... hmmm....

  10. #10
    Lee L's Avatar
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    DiCicco still works at Sky and Telescope magazine, and would probably answer questions about techniques for analemma shots, including the streaking sun at Dec 22nd, June 21st, and dates nearer equinox when the equation of time is at zero (where the figure 8 "crosses itself"), which could have been either mid-April or early September.

    You can likely find a way to contact him at the magazine web site:
    http://www.skyandtelescope.com/

    Lee

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