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Posted on 10/01/2004 8:58:17 PM PDT by ckilmer
Biggest Pinhole Camera Ever
Summary - (Oct 1, 2004) A common science experiment for young kids is to build a pinhole camera. Researchers from the University of Colorado at Boulder think NASA should build a gigantic one in space and use it to find planets orbiting other stars. The "New Worlds Imager" would be a football field-sized opaque light shade with a small opening right at the centre to let light through. A detector spacecraft would sit thousands of kilometres back and collect the light that comes through the opening. The shade would block the light from the star and let astronomers detect planets orbiting it. The proposal was one of 12 advanced concepts recently selected for further study by NASA.
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(Excerpt) Read more at biggest-pinhole-camera-ever.v3.net ...
Good point about the alignment problem too. We would have to have two mechanisms in space, not worrying about diffraction limits or light scattering effects you would have to keep these things in perfect alignment. Here is a paragraph from Space Telescope Science Institutes website describing the stability of the Hubble Telescope;
"Telescope stability: Hubble is the most precisely pointed
machine ever devised for astronomy. Its requirements for
pointing stability and pointing accuracy are expressed in
terms of multiple-zero decimals. The telescope must be able
to maintain lock on a target for 24 hours without deviating
more than 7/1,000ths (0.007) of an arc second (2 millionths
of a degree) which is about the width of a human hair seen at a
distance of a mile. A laser with the stability and precision
of the Hubble, mounted on top of the United States
Capitol could hold a steady beam on a dime suspended over
the World Trade Center in New York, over 200 miles distant.
This level of stability and precision is comparable to sinking
a hole-in-one on a Los Angeles golf course from a tee in
Washington, DC, over 2,000 miles away, in 19 out of 20 attempts."
I think looking at this device as a "giant pinhole camera" would be an enormous oversimplification of the technology involved to actually achieve a working device.
Yes, but they take GREAT pictures. We built an outdoor education unit out of pinhole photography when I was in collage.
I wouldn't rule out anything as impossible, I'm not an expert, just an amateur photographer. It just looks to me that its like putting a $2000 paint job on a $300 pickup truck. There seems to be a lot better ways of accomplishing the same thing.
Incidently, have you ever looked through a pinhole at a distance of a half-inch or so? Weird the way the field of view is much larger than it would seem like it should be.
I can see that you're thinking. That's a good thing.
To extend your thought consider your situation as you observe the night sky. It's exactly the same as Neal Armstrong's situation on the moon. You are looking through space that is filled with light. It's just not aimed at you. Light is invisible! Everything you know is WRONG!
I can’t argue with that. The idea is interesting, but not practical.
It will be a sad day indeed when Hubble “dies”. Even though its successor, the James Webb Space Telescope will be quite capable, nothing will ever replace the telescope that they said would never work.
Here’s some cool pinhole images: http://users.rcn.com/stewoody/index.htm
Now you've gone and done it! Bear in mind that it's 2am here on the east coast.
I'll have to think about that one in tomorrow.
“To extend your thought consider your situation as you observe the night sky. It's exactly the same as Neal Armstrong's situation on the moon.”
Wait a minute, Doc. For that to be true, wouldn't Armstrong have had to be on the “Dark Side” of the moon?
That's like saying, "not worrying about the 10 foot thick brick wall in my way" ... I'll just prance on down the road.
I agree.
Ahh, but on to the bigger question. Is light a wave or a particle?
As I understand it, your correct.
Quickly, what is a tachyon?
That depends on the definition of "exactly" :-)
You know, to be in exactly the same situation, he'd have to be standing in exactly the same spot as you!
With regard to the observation of a dark sky, he is in exactly the same situation as you ( at night ) because he is looking through the same space that you are looking through. In his case, the elevation of the sun above the horizon is immaterial, since there is no atmosphere.
During nighttime on the earth, we can of course observe a dark sky in exactly the same manner, since there is no intervening illuminated scattering medium, as there is during the daytime.
So, "exactly the same" means that in each case there is no intervening illuminated scattering medium.
To get more particular, I think that being on the moon during the day is similar to being on the earth at night in a brightly lit parking lot. The sky is dark, but the illuminated foreground makes the observation of the dark sky difficult.
Man! Twenty years ago I would love to have bounced this around. But, I'm getting a little lost in all of this now.
It's almost like we've gotten back to my first post (#14) in this thread.
But, hey! It's a mighty poor day that you don't learn something new.
Hmmm.
Your probably right, but I thought light had to be reflected in order to be "visible" and since space is a vacuum....
That's exactly right. This is a very difficult subject, you know. It's six dimensional! We have a three dimensional "k space" at every point of a three dimensional "configuration space" , i.e. space as you and I and Captain Kirk know it.
The point about an image plane for a pinhole is that it's exposed to all the starlight in the half of the sky to which it's exposed, assuming it's not exposed to the sun. It's all very intuitive, actually, if you can just sort it out.
A distant star shining through a pinhole is simply "masked" so that the illumination of the imaging surface is just the same as it would be without the pinhole, but confined to a spot which is the size of the pinhole. The brightness of the illumination is no greater than that from any other star which is visible from that spot. That's why the baffling is so important. It's also why the whole thing is such a stupid idea! The telescope was a great invention.
Purty damn sharp, aren't you?:)
I guess I don't get the trophy for being quick...
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