Post #176,567
9/27/04 12:13:27 PM
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The "stars"? Apparently Jupiter and Saturn.
[link|http://theastropages.com/articles/articles011.htm|Here] is more about the picture. (It was a linky in the APOD article on the picture.)
Cheers,
Scott.
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Post #176,570
9/27/04 12:26:17 PM
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Highly unlikely
The surface of the Earth has a brightness of, well, the surface of the Earth. This means a short exposure on slow film, and a near instantaneous one on fast film. Under these conditions, you would never see anything with your eyes other than the Moon and Sun, and perhaps Venus if you knew exactly where to look.
The Apollo astronaut commented on the near impossibility of seeing stars from the lunar surface. The eye stops down to a tiny hole. A typical camera setting would be 1/60th second at f22.
You can barely see some planets in pictures of the sky recorded during a total solar eclipse:
[link|http://www.mreclipse.com/TSE01reports/TSE01Espenak.html|http://www.mreclipse...TSE01Espenak.html]
Jupiter is faintly visible below and to the left of the Sun.
(The bright spots are probably reflections from each side of the thick window of the same light source inside Mir.)
-drl
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Post #176,574
9/27/04 12:38:03 PM
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It is possible
Jupiter is about 5.2 times as far from the Sun as the Earth. It is therefore about 1/27'th as bright there as at Earth. Assuming similar reflectiveness, Jupiter is a few percent of the brightness of the Earth and is much smaller.
I could see that being bright enough to show up as the pale spec that you see when film has no atmospheric effects to further dim it.
Of course if the astronomy programs did not say that it should be right there, then I wouldn't have guessed that answer...
Cheers,
Ben
About the use of language: it is impossible to sharpen a pencil with a blunt axe. It is equally vain to try to do it with ten blunt axes instead. -- Edsger W. Dijkstra
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Post #176,584
9/27/04 1:09:55 PM
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It's a good point
..that is, the apparent surface brightness is dependent only on the albedo and the distance from the light source. But 25 times dimmer is a *lot* dimmer - so that correctly exposing Earth means that Jupiter would appear as a dark gray pinpoint on the film.
A good exposure time for Jupiter is 1/30th second at f8 on ISO 400 film. Compare this to daylight Earth photography - 1/500th second at f8 on the same film.
Of course it's possible to exactly determine where Jupiter is, not approximately, something I'll do when I get home :)
-drl
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Post #176,581
9/27/04 12:56:22 PM
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Dunno.
They might have used a CCD camera for the picture. Also, the simulations seem to put the planets in the right place, according to the reports, so I think it's possible. Plus, I'm sure the photographers are aware of reflection issues and do what they can to avoid them.
The exposure issues are real, but I don't think they're insurmountable. E.g. the Pat Totten photo in your link. A photo of the Earth would have less light intensity than the photo of the corona making it less of an issue.
Cheers,
Scott.
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Post #176,585
9/27/04 1:13:39 PM
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Re: Dunno.
Eclipse photos are deceptive. It's *dark* during an eclipse, as at dusk. I remember the eclipse that passed over Atlanta in May of 1984, which was 99.7 percent total. I took some photos during the darkest time at the same f-stop and exposure as recommended for full daylight. They came out very dark - spookily so, because the eye adjusts and it doesn't seem that drastic.
-drl
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Post #176,690
9/28/04 3:39:06 AM
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What spooked me
I saw the recent partial eclipse.
Things had two shadows.
Weird.
Peter
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Post #176,770
9/28/04 11:58:26 AM
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Fun exercise in an eclipse
Hold both hands out, fingers slightly apart, turn your hands so that the fingers form a cross hatch pattern. Every spot where the light falls forms into a picture of the eclipse!
Better yet, go walking in a deciduous forest and admire the eclipses dancing on the ground.
Actually we're all very familiar with the phenomena. However we're used to seeing it with a picture of an uneclipsed Sun, and so seeing it with a different image is quite surprising.
Cheers,
Ben
About the use of language: it is impossible to sharpen a pencil with a blunt axe. It is equally vain to try to do it with ten blunt axes instead. -- Edsger W. Dijkstra
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Post #176,913
9/29/04 12:19:52 AM
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My dad has a photo of that.
Back in the mid-70's there was an eclipse that was visible in Sydney. Dad noticed all the eclipse shapes in the dappled shade of a tree and took a photo.
Incidentally, that phenomenon is related to how holograms work.
Wade
Is it enough to love
Is it enough to breathe
Somebody rip my heart out
And leave me here to bleed
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Is it enough to die
Somebody save my life
I'd rather be Anything but Ordinary
Please
| -- "Anything but Ordinary" by Avril Lavigne. |
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