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'Sky' skylight

 Rear projection upwards pointing camera obscura.
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A lense assembly projects an image of the sky onto the back of a diffuser in the ceiling. Instead of a simple bright square, your skylight would have moving images of birds and clouds on it. Very pretty.
—spidermother, Feb 02 2006

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       I want this to view the clear night stars . The diffuser would be a shallow 1m dish on the ceiling . If the diffuser was removed and the room blacked out then the starlight would play all around the room . Good for romantic dinners .   

       I was wondering, since light is an electromagnetic phenomenon, could a travelling wave tube be use to amplify the impulses received to gain a better projection . Of course this implementation would have to be plugged in and switched on . There would also be the big kink in the camera obscura to hide .
—wjt, Jan 23 2009
   

       I hadn't imagined any amplification, as part of the goal was to take advantage of natural light. If electric or similar energy were used to increase the light it would (in my opinion) defeat the purpose; you might as well use an electronic camera and screen or projector.   

       The prospect of amplifying light in the manner you suggest sounds interesting; I gather such things are done in fibre optics, using laser-like principles.
—spidermother, Jan 25 2009
   

       I may be wrong but a travelling wave tube wouldn't raster/pixelate like an electronic camera . The light waves would be all natural but increased .
—wjt, Jan 26 2009
   

       I may also be wrong, but a travelling-wave tube seems to take a single modulated RF input, and amplify it; to amplify an image would require an array of them, so the image would be pixelated. I also can't find evidence that it would work with visible light. Maybe you could create a cosmic microwave background radiation 'sky' skylight. In that case, the large wavelengths might make pixellation a non-issue.
—spidermother, Jan 26 2009
   

       Sorry my bad . I was imagining(hopeful) a travelling wave tube that could handle the visible range (400–790 terahertz) .   

       Wikipedia stated that the range was a broadband as high as 3 octaves . Doesn't that mean it will amplify all the RF frequencies in that range . If the TWT can do a band of frequencies then possibly only one is needed, no pixellation .   

       A cosmic background skylight might look abit like a mathmos light but maybe bit slower .
—wjt, Jan 29 2009
   

       Over my head... But, what I see happening is a projection of the natural overhead light, birds and all, right into the room. Which is cool. But, I can't actually see most of the birds anyways when I go outdoors, whats the point? I need a computer to look for birds, find them, focus on them, and project their light into my room for big bird action! Thanks!
—daseva, Jun 21 2009
   

       I don't feel like waiting another most of a month.   

       I did some calculations, and if we assume: 1. a collecting lens diameter of 100 mm, 2. a medium sunlight illuminance of 40 klx, 3. an optical efficiency of 60% (CandlePowerForums rule of thumb for flashlight optics—might be a bit high for this), and 4. a 1 m diameter circular diffuser, then the diffuser will be illuminated at 240 lux, but maybe only half of that (depending on material) will be diffused in the direction of the room, so you'd get about a 120 lux image, which would probably be somewhat visible indoors even with the lights on. At night, you'd need the lights off, and you might need a bigger collecting lens for it to be really good.   

       // If the TWT can do a band of frequencies then possibly only one is needed, no pixellation . //   

       How do you conclude that? Having a high bandwidth in temporal frequencies doesn't imply the same in spatial frequencies.   

       // A cosmic background skylight might look abit like a mathmos light but maybe bit slower . //   

       There's that word again! Wiktionary is still only defining it as a nickname for mathematicians, and that doesn't make sense here.
—notexactly, May 28 2019
   

       I imagined the workings of such a device today, but alas, here it is 15 years ago. Sigh.   

       Bun [+]
—whatrock, Aug 06 2021
   
      
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