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| David Findlay... |
 Posted: Wed Oct 28, 2009 9:23 pm |
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As I understand it the Apollo 11 tv camera was installed upside down on it's
mount, and the initial picture of Neil Armstrong coming down the ladder was
upside down. They flipped it over in seconds though on the TV coverage.
This isn't strictly a spaceflight question, but I'm curious as to how they
were able to flip or rotate a TV picture in 1969. It's easy now with
digital technology. I'm not too knowledgeable about analogue TV
electronics. Can anyone explain to me how it was done? Thanks,
David |
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| Rusty Shackelford... |
| Posted: Wed Oct 28, 2009 11:10 pm |
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David Findlay wrote:
[quote]As I understand it the Apollo 11 tv camera was installed upside down on it's
mount, and the initial picture of Neil Armstrong coming down the ladder was
upside down. They flipped it over in seconds though on the TV coverage.
This isn't strictly a spaceflight question, but I'm curious as to how they
were able to flip or rotate a TV picture in 1969. It's easy now with
digital technology. I'm not too knowledgeable about analogue TV
electronics. Can anyone explain to me how it was done? Thanks,
David
[/quote]
It's actually even easy to do with an analog scan TV. Instead of
scanning the CRT from left to right from the top down, scan from right
to left from the bottom up. No big deal really and I'm pretty sure they
did have just such a button to flip the scan direction over on their system.
Not to mention that the scan rate conversion scheme was so primitive -
they pointed a vidicon 30 fps camera at a B&W slow phosphor CRT that
displayed the 10 fps video coming down from the moon. The could have
simply rotated the vidicon 180 degrees if they so desired (but I don't
think this is actually what they did, they were prepared to invert the
scan direction). |
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| OM... |
| Posted: Wed Oct 28, 2009 11:22 pm |
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On Thu, 29 Oct 2009 13:23:45 +1000, David Findlay
<david at (no spam) davsoft.com.au> wrote:
[quote]As I understand it the Apollo 11 tv camera was installed upside down on it's
mount, and the initial picture of Neil Armstrong coming down the ladder was
upside down. They flipped it over in seconds though on the TV coverage.
This isn't strictly a spaceflight question, but I'm curious as to how they
were able to flip or rotate a TV picture in 1969. It's easy now with
digital technology. I'm not too knowledgeable about analogue TV
electronics. Can anyone explain to me how it was done? Thanks,
[/quote]
....Just as simple with Analog as it is with Digital. Just invert the
incoming horizontal and vertical sync pulses so that the picture is
rotated 180 degrees. Interestingly enough, about 1/10th of the color
TVs and something like 80% of the B&W models manufactured prior to
1977 - before TV manufacturers started using ICs in the tuners to
provide Phase Locked Loop frequency stabilization - have a switch,
jumper or at least a trace on the mainboard that will allow for a TV
repair crook to flip the picture in this way, as well as another to
flip by just the vertical axis. The latter flip allowed any TV with
such a circuit to be used as a teleprompter by reversing the picture
so that text reflected off a see-thru mirror could be read by the news
anchor(s).
As far as computer monitors go, I'm not sure how widespread either
switching was implemented, because it's been pretty easy to flip the
display using the PC...
OM
--
]=====================================[
] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
] an obnoxious opinion in your day! [
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| David Findlay... |
| Posted: Wed Oct 28, 2009 11:38 pm |
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[quote]It's actually even easy to do with an analog scan TV. Instead of
scanning the CRT from left to right from the top down, scan from right
to left from the bottom up. No big deal really and I'm pretty sure they
did have just such a button to flip the scan direction over on their
system.
[/quote]
Of course. I just hadn't thought of the the phosphor scanning the opposite
way to normal. How silly of me. Thanks!
David |
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| David Findlay... |
| Posted: Wed Oct 28, 2009 11:38 pm |
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Guest
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[quote]...Just as simple with Analog as it is with Digital. Just invert the
incoming horizontal and vertical sync pulses so that the picture is
rotated 180 degrees. Interestingly enough, about 1/10th of the color
TVs and something like 80% of the B&W models manufactured prior to
1977 - before TV manufacturers started using ICs in the tuners to
provide Phase Locked Loop frequency stabilization - have a switch,
jumper or at least a trace on the mainboard that will allow for a TV
repair crook to flip the picture in this way, as well as another to
flip by just the vertical axis. The latter flip allowed any TV with
such a circuit to be used as a teleprompter by reversing the picture
so that text reflected off a see-thru mirror could be read by the news
anchor(s).
[/quote]
Thanks, makes sense now.. Thanks,
David |
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