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  1. #1

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    How fast does the moon move through the sky

    I'm working on a picture that will include the moon. I'm using an 85mm lens on 35mm film. Problem is the exposure on TMAX 100 will need to be 15-20 seconds. TMY2 would obviously help, but I would really rather use TMX for finer grain. As fine grained as TMY2 is, I would really rather use TMX if I can. So my question is, how short does an exposure have to be to keep the moon sharp? It seems to move pretty damn fast, especially when I'm setting up and it speeds up so I miss the shot

    I guess ideally I'd make a first exposure for the scene before the moon is in frame, and then just add a short second exposure when the moon is in place. But I can never rely on double exposures with a roll film camera. Too bad I won't be able to use sheet film for this one.
    Last edited by Michael R 1974; 06-16-2011 at 01:17 PM. Click to view previous post history.

  2. #2

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    Moon orbits around the earth in 27 days. So I'd imagine most of the "movement" of the moon is actually the rotation of the earth itself... which will be 24 hours per cycle.

    According to the ever reliable wiki page, it says it moves at around 0.5 degrees per hour.

    http://en.wikipedia.org/wiki/Orbit_of_the_Moon
    Develop, stop, fix.... wait.... where's my film?

  3. #3

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    I'm ok on the physics. But I'm not sure how to translate it to photography and how long one could keep the shutter open with an 85mm lens (probably can assume 50mm or "0 magnification") before blurring would become visible.

  4. #4
    ann
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    The moon is quite bright, remember it is lite from the sun. Frankly I have my students rate the film at ISO 200, a shutter speed of 250 at f5.6 or F8; so, just reduce one of those by 1stop to reflex a reduction of 1 stop of ISO
    http://www.aclancyphotography.com

  5. #5

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    With 85mm lens, the moon will basically appear as a dot. There won't be much detail to speak of at all. Also, moon is very bright. Depending on your aperture setting, it will bloom quite a bit further obscuring details.

    According to the Wiki page, it moves just about its diameter per hour. That means if you kept the shutter open for a whole minute, it will move 60th of its diameter.

    How large are you going to print this?
    Develop, stop, fix.... wait.... where's my film?

  6. #6
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    I once did a setup where I wanted to have the moon traverse most of the diagonal of the 135 frame. I didn't have a long lens so I was tring to get creative

    I cant remember the specifics but I think the exposures were in the 20 minute range.

    I screwed around with the whole roll and remember I surprised how much it did move even with shorter exposures. The shorter exposures didn't work too well, the moon was just blurred with no detail.

    I'm sorry I can't help more but at least you recongnize there will be some movement.
    Good luck and share your results.
    Last edited by brucemuir; 06-16-2011 at 01:43 PM. Click to view previous post history. Reason: clarification, spelling

  7. #7

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    Quote Originally Posted by tkamiya View Post
    With 85mm lens, the moon will basically appear as a dot. There won't be much detail to speak of at all. Also, moon is very bright. Depending on your aperture setting, it will bloom quite a bit further obscuring details.

    According to the Wiki page, it moves just about its diameter per hour. That means if you kept the shutter open for a whole minute, it will move 60th of its diameter.

    How large are you going to print this?
    Likely not larger than 8x10". With a normal lens it will be more than a dot. Detail is definitely visible and it is larger than one might expect in the frame. The luminance of the moon will fall initially on zone X with the exposure I'm giving because the foreground elements are quite dark. Even with exposure on zone X there won't be much bloom and full detail will be recorded.

  8. #8
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    This free photography planning tool might be useful? I use it all the time planning my landscape photos. It has loads of info about the position of the sun and moon position:
    http://photoephemeris.com/

  9. #9

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    Quote Originally Posted by brucemuir View Post
    I once did a setup where I wanted to have the moon traverse most of the diagonal of the 135 frame. I didn't have a long lens so I was tring to get creative

    I cant remember the specifics but I think the exposures were in the 20 minute range.

    I screwed around with the whole roll and remember I surprised how much it did move even with shorter exposures. The shorter exposures didn't work too well, the moon was just blurred with no detail.

    I'm sorry I can't help more but at least you recongnize there will be some movement.
    Good luck and share your results.
    Thanks. Yes it does move quite fast. I might have to experiment with a scrap roll and just try some exposures at various times between 4 seconds and 20 seconds. I guess that's the only way to know for sure whether I need to use TMY2 or can stick with TMX.

  10. #10

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    Kodak had an article in one of their photo-guides about shooting a series of just the full moon. The moon was always in the upper right portion of the frame. Later the film was reloaded making a double exposure to have a large moon in the scene.
    Their top camera at the time was the Retina Reflex IV. The 200 mm f 4 was the lens used for the moon and a 50 or 35 for the second exposure. The film was Kodachrome 64 and the exposure on a full moon was 1/60 @ f4. The maximum on the 200 lens.

    Francis in VT

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