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Post by forthethrillofital on Feb 6, 2012 17:00:15 GMT -4
I also think the OP is trying to point out that the astronauts would be required to document the positions of the stars relative to the moon horizon... No, sighting stars relative to the local lunar surface horizon doesn't give you useful data. What makes you think the astronauts would be able to see such a laser? I was under the impression sighting the stars and horizon and knowing the exact time of day on the moon would give the astronauts the location. I read the Apollo 11 astronauts carried a star chart down to the surface of the moon for this reason. I read this chart was time sensitive and would be fairly accurate if used within the first two hours of the landing. Is that incorrect? I may be wrong about this but believe I read the chart was actually sold. I know that seems crazy to sell something like that. But I did read this or at least think I did somewhere. I have read that blue-green lasers are visible generally and that surveyor 7 imaged an earth blue-green laser from the surface of the moon with a television camera. This was done in early 1968. A girl friend of mine showed me a part of the exchange between the Apollo 11 astronatuts and the Houston based controllers where the controllers were trying to get the astronauts to visualize an earth laser coming from an observatory in Texas. She also had a NY Times newspaper clip that indicated they were using the Texas blue-green laser duiring the Apollo 11 expedition and were hoping the astronauts would be able to see the laser from the surface of the moon. The little pieces I read indicated that the people on earth at least thought the astronauts should be able to see the blue-green laser. Our eyes are blue-green sensitive and so for me it all added up. I read that the scientists doing the Apollo 11 expedition laser experiments also used red lasers. I found nothing specific on these but gathered red laser light is not as visible as blue-green laser light primarily for physiologic reasons. However I do not know that for a fact. It seemed to be inferred in the pieces I read about laser light. |
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Post by JayUtah on Feb 6, 2012 17:06:36 GMT -4
I was under the impression sighting the stars and horizon and knowing the exact time of day on the moon would give the astronauts the location. Your impression is wrong. Elevation angles measured from a local terrestrial horizon are worthless. That's basic navigation. Everything is visible generally. What makes you think astronauts could have seen it with the naked eye? And why are all your references vague? |
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Post by forthethrillofital on Feb 6, 2012 17:18:50 GMT -4
I was under the impression sighting the stars and horizon and knowing the exact time of day on the moon would give the astronauts the location. Your impression is wrong. Elevation angles measured from a local terrestrial horizon are worthless. That's basic navigation. Everything is visible generally. What makes you think astronauts could have seen it with the naked eye? And why are all your references vague? The part about the astronauts being asked to see the laser from space is not vague. It is easy to find. Just enter "laser" into the Apollo 11 communication PDF. The search will bring it right up. You can do the same with the NY Times article. At least I believe my girlfriend found it with a simple NY Times archive search using "laser" and "Apollo" as keywords. I can ask my girlfriend to give me the date. |
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Post by forthethrillofital on Feb 6, 2012 17:22:50 GMT -4
I was under the impression sighting the stars and horizon and knowing the exact time of day on the moon would give the astronauts the location. Your impression is wrong. Elevation angles measured from a local terrestrial horizon are worthless. That's basic navigation. Everything is visible generally. What makes you think astronauts could have seen it with the naked eye? And why are all your references vague? Why did Aldrin say that the star chart was important to them then? The only conceivable reason for it to have been carried was for help with sighting stars. They need to sight stars to determine the orientation of the guidance system. If it is precise enough to do that then the method should be precise enough for them to locate themselves. |
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Post by JayUtah on Feb 6, 2012 17:24:04 GMT -4
Why are your references still vague?
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Post by JayUtah on Feb 6, 2012 17:26:03 GMT -4
Why did Aldrin say that the star chart was important to them then? What does Aldrin's comment have to do with measuring the elevation of stars above a terrestrial horizon? You can measure elevation above the horizon at sea, but that's irrelevant to the Moon. |
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Post by Tanalia on Feb 6, 2012 19:49:08 GMT -4
They need to sight stars to determine the orientation of the guidance system. If it is precise enough to do that then the method should be precise enough for them to locate themselves. (Emphasis added) Orientation and location are entirely different things. |
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Post by JayUtah on Feb 6, 2012 20:07:30 GMT -4
They need to sight stars to determine the orientation of the guidance system. If it is precise enough to do that then the method should be precise enough for them to locate themselves. No, you're making the same elementary mistake as the OP. Orientation does not give you this. Nor does orientation plus a gravity-vector value. A star sight plus a gravity vector plus time can give you a rough guess of where you are on the lunar surface. The star sight is not equivalent to an orientation, and the method works because both the star sight and the gravity vector are reckoned according to the spacecraft's reference frame. |
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Post by Jason Thompson on Feb 7, 2012 4:33:25 GMT -4
the moon had been so well mapped that if precise coordinates had been provided they would not correspond to what was seen on television that evening. And just what was that? In another post you described the Apollo 11 landscape as 'generic nothing'. The Sea of Tranquility is a very large expanse of pretty well nothing. How precise would the co-ordinates have to have been to make the 'generic nothing' seen on the TV screen match another bit of 'generic nothing' elsewhere in the flat plain that is few hundred miles across? No it would not. For one thing a land horizon is rarely a true horizon. That method of navigation was only ever used on the sea, where you had a true horizon devoid of landmarks and hills and valleys. |
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Post by Jason Thompson on Feb 7, 2012 4:37:17 GMT -4
Why did Aldrin say that the star chart was important to them then? The only conceivable reason for it to have been carried was for help with sighting stars. They need to sight stars to determine the orientation of the guidance system. If it is precise enough to do that then the method should be precise enough for them to locate themselves. Why does a precise method of working out which way you are facing tell you exactly where you are? I can orient myself facing north very very easily by sighting stars. If I know the time and where those stars should be I can then use that information to orient myself in any given direction. That's the easy bit. Now how precisely can I then locate my position on the surface of the Earth? Or, to put it another way, how far would I have to move from my current position in order for the stars to appear sufficiently different for me to identify that I had moved? And here's the best bit about that question: you can actually go out and do this for yourself on any clear night. Go out and learn the difference between working out which way you are facing and where you are located. It shouldn't be too hard to do. We'll await your results from this simple experiment you and your girlfriends can do easily. |
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Post by forthethrillofital on Feb 7, 2012 6:03:10 GMT -4
Deleted, unauthorized access
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Feb 7, 2012 9:50:10 GMT -4
I do not read the OP's main point that way at all. Admittedly I am not as familiar with some of these details as you seem to be. Still I think his(her?) point is that the moon had been so well mapped that if precise coordinates had been provided they would not correspond to what was seen on television that evening. I also think the OP is trying to point out that the astronauts would be required to document the positions of the stars relative to the moon horizon and given the time this would precisely determine location. Any time you attempt to describe the OP's main point it is important to cite the epoch, due to the constantly changing nature of his arguments. |
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Post by twik on Feb 7, 2012 10:55:40 GMT -4
Why did Aldrin say that the star chart was important to them then? The only conceivable reason for it to have been carried was for help with sighting stars. They need to sight stars to determine the orientation of the guidance system. If it is precise enough to do that then the method should be precise enough for them to locate themselves. Why does a precise method of working out which way you are facing tell you exactly where you are? Reminds me of the little filler ad on one of the science channels, about how to use the sun to find south if you're lost in the woods. It ends up "Congratulation! You're now lost in the woods, facing south". |
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Post by twik on Feb 7, 2012 11:00:01 GMT -4
At least I believe my girlfriend found it with a simple NY Times archive search using "laser" and "Apollo" as keywords. I can ask my girlfriend to give me the date. If it's so easy to pull up, why don't you do it, rather than asking your hypothetical GF? You're sitting at the computer right now! |
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Post by twik on Feb 7, 2012 11:21:48 GMT -4
I do not read the OP's main point that way at all. Admittedly I am not as familiar with some of these details as you seem to be. Still I think his(her?) point is that the moon had been so well mapped that if precise coordinates had been provided they would not correspond to what was seen on television that evening. I also think the OP is trying to point out that the astronauts would be required to document the positions of the stars relative to the moon horizon and given the time this would precisely determine location. OK, if the area of the Moon has been so well mapped, why couldn't NASA (who in your view managed to create a method for filming things on earth that completely simulated 1/6 gravity, in a vacuum) have created a set that matched those details? This the same sort of poorly thought-out argument as that regarding why NASA "had to" leave out stars from photographs. The argument was that stars on the Moon should "look different" from stars on the Earth (not true, but let's go with it a moment), and even amateur astronomers would notice immediately. When JayUtah and others asked why NASA couldn't just have replicated the star pattern that *should* be seen, the answer becomes "Oh, that's far too complicated to calculate". So, NASA - an organization that even its distractors must admit has a fairly large staff of people knowledgable about astronomy - cannot replicate what is expected to be seen in a real mission, but the average Joe watching TV would immedately know what was wrong with it? |
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