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Post by echard on Aug 31, 2008 19:31:35 GMT -4
You all are a great source of knowledge and insightful explanations. I need to draw on that again unfortunately. I've come across a YouTube video showing a portion of the Mythbusters episode where for a brief moment, two lines appear from the astronauts to the top of the screen. As you can imagine, the hoaxers believe they've found the next undebunkable "proof", and I'd love to explain exactly what it is we're seeing. While I hate posting links to YouTube videos, you need to see it to understand what I'm talking about. As you'll see, the "wires" don't appear to connect to the PLSS antenna but to another part of the pack. www.youtube.com/watch?v=UmIWhzTzLn0Now I know they're not wires, but what would cause such an artifact to appear like that? Do you know of any other instances where the same type of artifact exists apart from where the astronauts are located? Thanks in advance for any information you've got. |
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Post by Czero 101 on Aug 31, 2008 20:05:30 GMT -4
Its just an artifact on the video caused by the type of video camera used on the Moon.
Notice that it occurs right after a reflective flash off the antenna on the PLSS. Most people - HB's especially - don't know how the video camera the astronauts used actually worked. They just think its the same type of camera that they can buy at Future shop or that are used in today's tv studios or film sets.
I don't have the technical know-how to explain in any great detail how the Lunar video camera worked (I'm sure othjers will be more than able to do that), but I know that they used a colour-wheel and a b/w vidicon tube to create separate images which were then sent to Earth and recombined after processing to create a colour image. This is why you sometimes see what appear to be "ghost images" in the video when the astronauts or other objects in frame are moving around.
Again, I'm sure there will be someone else along shortly to explain in greater technical detail.
Cz
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Post by Count Zero on Aug 31, 2008 20:38:04 GMT -4
Well, for starters, the wires that professionals use on flying rigs don't reflect light. Glinting wires are difficult to hide, so the industry standard on flying rigs has (for the better part of a century) used non-reflective wires.
Another ignorant "fail" for the HBs.
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Post by JayUtah on Aug 31, 2008 21:13:47 GMT -4
The Mythbuster footage is a kinescope. The "glints" are vertical scratches in the film.
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Post by echard on Aug 31, 2008 21:49:35 GMT -4
Does anybody know the mission/EVA for this video? I'd like to view a better copy to see if the scratches extend through the astronauts to the bottom of the frame.
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Post by JayUtah on Aug 31, 2008 22:15:22 GMT -4
My gut says it's Apollo 16, but it's been wrong before. I don't have a definite cite for it. It's naturally important to find a good source, but keep in mind that you really need to find the exact source that the Mythbusters used. I'll see what I can do.
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Post by dwight on Sept 1, 2008 9:49:32 GMT -4
Hey, I finally earned an "I corrected Jay" T-shirt!! Woo hoo! Although I think I just scraped through thanks to his almost-a-disclaimer.
The snippet is from Apollo 17 at the ALSEP station. For those with the SCF DVD set. It is on Disc 2, Title 3 Chapter 12 at around 1hr 47. The segment is most definitely kinescope and the scratches are not as pronounced as the mythbuster source. In fact I had trouble finding them.
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Post by dwight on Sept 1, 2008 13:04:59 GMT -4
Cz you are correct. The TV camera (in this case the GCTA RCA camera) had essentially a black and white camera tube with a rotating mechanical wheel in front of the pickup tube with the following filters: Red Blue Green Red Blue Green.
A synch pulse triggered by the spinning wheel allowed ground stations to know which filter was being used, and could subsequently begin the following:
The signal was sent via the LCRU to the "umbrella" on the LRV which was the transmitter back to earth. Using a bore-sight type setup the astronauts had aligned the antenna to face the earth. Ground stations at Honeysuckle/Tidbinbilla, Madrid; and Goldstone received the signal which was first sent through a tape loop system which removed any doppler distortion and synched, via analog means, the signal to standard 525/60 TV. The signal was then sent to a custom built (by CBS labs) video disk recorder which stored each frame into a buffer and then mixed the red blue and green together from sequential frames to form a colour NTSC compatible signal. This was then sent to mission control and also to the networks. Almost forgot: John Lowry also cleaned up the image to remove alot of noise prior to the signal going to Houston. The kinescopes were made in the early 1970's mainly because the National Archives did not accept a non-film based medium to be archived. Thus all complete Apollo downlinks held at the Archives are kinescope, whereas those held by CBS would be their own 2" videotape.
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Post by smlbstcbr on Sept 1, 2008 22:21:33 GMT -4
Cz you are correct. The TV camera (in this case the GCTA RCA camera) had essentially a black and white camera tube with a rotating mechanical wheel in front of the pickup tube with the following filters: Red Blue Green Red Blue Green. A synch pulse triggered by the spinning wheel allowed ground stations to know which filter was being used, and could subsequently begin the following: The signal was sent via the LCRU to the "umbrella" on the LRV which was the transmitter back to earth. Using a bore-sight type setup the astronauts had aligned the antenna to face the earth. Ground stations at Honeysuckle/Tidbinbilla, Madrid; and Goldstone received the signal which was first sent through a tape loop system which removed any doppler distortion and synched, via analog means, the signal to standard 525/60 TV. The signal was then sent to a custom built (by CBS labs) video disk recorder which stored each frame into a buffer and then mixed the red blue and green together from sequential frames to form a colour NTSC compatible signal. This was then sent to mission control and also to the networks. Almost forgot: John Lowry also cleaned up the image to remove alot of noise prior to the signal going to Houston. The kinescopes were made in the early 1970's mainly because the National Archives did not accept a non-film based medium to be archived. Thus all complete Apollo downlinks held at the Archives are kinescope, whereas those held by CBS would be their own 2" videotape. That's using the brain hard. An incredible way of transmitting color video over a very narrow bandwidth, didn't know this. It makes me angry to think that the HB discredit all the engineering behind the Apollo program. They will burn in hell... |
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raven
Jupiter
That ain't Earth, kiddies.
Posts: 509
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Post by raven on Sept 2, 2008 2:31:23 GMT -4
Another advantage to such a system, was that it didn't require the three colour tubes that an ordinary colour video camera of the time would have required, a reduction of weight by about 2/3rds I would imagine, not mention the power savings as well.
I have a better idea, put them in a magic cavern at the 1/6th gravity depth. About equivalent would be my guess. ;D
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Post by Kiwi on Sept 2, 2008 6:57:40 GMT -4
This post has an analysis of one of the flashes during Apollo 17 that HBs trot out as "evidence" of wires. It also gives the details for finding the flash on the Spacecraft Films' DVDs.
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Post by smlbstcbr on Sept 2, 2008 10:27:18 GMT -4
Another advantage to such a system, was that it didn't require the three colour tubes that an ordinary colour video camera of the time would have required, a reduction of weight by about 2/3rds I would imagine, not mention the power savings as well. I have a better idea, put them in a magic cavern at the 1/6th gravity depth. About equivalent would be my guess. ;D ;D Or we could put them in that paper-bag-filled-with-helium set...  |
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Post by Count Zero on Sept 2, 2008 14:29:43 GMT -4
How 'bout a hydrogen-filled set?
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Post by echnaton on Sept 2, 2008 16:18:48 GMT -4
Well the Mythbuster's do enjoy a good explosion now and then.
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raven
Jupiter
That ain't Earth, kiddies.
Posts: 509
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Post by raven on Sept 2, 2008 17:27:46 GMT -4
As do the viewers. ;D
My favorite still has to be the time the cement truck went boom.
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