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Apollo shadows explanation? (Was: Off to the moon!)
Brian Sandle wrote:
But one thing I need to look into better is this sort of effect: Have you been at a sports field at night with one mercury lamp going? The shadows are much sharper than what the sun makes. The sports field lamp is more of a pin point source than the sun. The sunlight shadows get more blurry the further from the shadowed object. That effect is much less with the sports field lamp - the shadows stay sharp. Do any of the videos under discussion allow analysis? I can't see the shadows getting more blurry further away. I have been looking at some pictures from the image database section of our public library's Ebscohost online database. There is a photo of Apollo 14 astronaut Alan Shepard holding a flag upright on the moon. Now I agree the shadow of the landing vehicle has umbra and penumbra. But the shadow of the flag pole I would have expected to have less penumbra near its base and more higher up. Also I note an interruption of the pole's shadow just below the shadow of the hand of Alan. Any ideas? Any comments on the earlier Apollo photo shadows? |
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Apollo shadows explanation?
In sci.space.policy Brian Sandle wrote:
Brian Sandle wrote: But one thing I need to look into better is this sort of effect: Have you been at a sports field at night with one mercury lamp going? The shadows are much sharper than what the sun makes. The sports field lamp is more of a pin point source than the sun. The sunlight shadows get more blurry the further from the shadowed object. That effect is much less with the sports field lamp - the shadows stay sharp. Do any of the videos under discussion allow analysis? I can't see the shadows getting more blurry further away. I have been looking at some pictures from the image database section of our public library's Ebscohost online database. There is a photo of Apollo 14 astronaut Alan Shepard holding a flag upright on the moon. Now I agree the shadow of the landing vehicle has umbra and penumbra. But the shadow of the flag pole I would have expected to have less penumbra near its base and more higher up. When I look at a shadow of a vertical broom handle, one end on the ground, with the sun at about 45 degrees then the umbra is the whole width of the handle near it, but further away it gets to only about half, with the rest penumbra. Also I note an interruption of the pole's shadow just below the shadow of the hand of Alan. What change in level of ground would cause that sudden increase of more than 50 percent distance of shadow from pole? |
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