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  #1  
Old 24 February 2007, 06:08 AM
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ganzfeld ganzfeld is offline
 
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Crash Star pair in Ursa Major a traditional test of sight?

Next to the star Mizar in Ursa Major (the Big Dipper) is a dimmer star called Alcor. The two don't form a binary system (although they happen to each be multiple-star systems) but on most nights and to most eyes they appear to be one star. (Please correct me if any of this is wrong.)

The story that is often told about them is that they were used as a test of vision for "warriors". If you could see Alcor, you had good vision. I'm wondering if anyone knows where the claim originally comes from and if there is any evidence that it predates the invention of the telescope.

Ganz

(I seem to recall reading/posting about this on a much earlier thread so chow away if you can find that.)
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  #2  
Old 24 February 2007, 01:21 PM
lazerus the duck
 
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I could see it being used but wouldn't it be just as easy to say see that sheep over there. It just seems there are lots of easier ways to judge someones eyesight.
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  #3  
Old 24 February 2007, 09:18 PM
Nick Theodorakis Nick Theodorakis is offline
 
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I can see them, and I don't think my vision is particularly good, even after correction.

This page says it's a test for "minimal vision."

Nick
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  #4  
Old 25 February 2007, 02:40 AM
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Silas Sparkhammer Silas Sparkhammer is offline
 
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Quote:
Originally Posted by lazerus the duck View Post
I could see it being used but wouldn't it be just as easy to say see that sheep over there. It just seems there are lots of easier ways to judge someones eyesight.
Actually, there are very few such absolutely objective tests, tests that are the same for everyone, everywhere. e.g., "can you see a fly on a pig's back at 100 yards?" What kind of fly, what color pig, and whose "yards?" All very different. But "can you see Mizar and Alcor?" is pretty much objective.

I have heard it said that some people have vision so acute they can make out the Galilean satellites of Jupiter; this, for some reason, I have difficulty accepting.

By the way, Mizar itself is the first star that was revealed by photography to be binary.

Silas
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  #5  
Old 25 February 2007, 03:10 AM
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ganzfeld ganzfeld is offline
 
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Originally Posted by Silas Sparkhammer View Post
By the way, Mizar itself is the first star that was revealed by photography to be binary.
More recently, each of these stars, Mizar A and Mizar B were revealed through spectrometry to each be binary stars, meaning the system has at least four stars (not inclduding Alcor, which is very close but not known to be part of the system AFAIK).
http://apod.nasa.gov/apod/ap970219.html
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Originally Posted by Silas Sparkhammer View Post
Actually, there are very few such absolutely objective tests, tests that are the same for everyone, everywhere. e.g., "can you see a fly on a pig's back at 100 yards?" What kind of fly, what color pig, and whose "yards?" All very different. But "can you see Mizar and Alcor?" is pretty much objective.
My problem with this is that the visibility of the pair is so different in different parts of the world, different times of the year/night and, most importantly, during different weather. I guess in places where you get the same kind of clear nights many times it would be a good test. (Perhaps, living in Japan and having grown up on the East Coast of the US, I simply have no experience with that!)
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  #6  
Old 25 February 2007, 11:12 AM
lazerus the duck
 
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Quote:
Originally Posted by Silas Sparkhammer View Post
Actually, there are very few such absolutely objective tests, tests that are the same for everyone, everywhere. e.g., "can you see a fly on a pig's back at 100 yards?" What kind of fly, what color pig, and whose "yards?" All very different. But "can you see Mizar and Alcor?" is pretty much objective.
That's what I have a problem with, why would a warrior need such a test, even a trained archer would not need such an absolute test. Seems too complex and romanticised when there are such simpler solutions.
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  #7  
Old 25 February 2007, 01:29 PM
Traveler in Black
 
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Originally Posted by ganzfeld View Post
My problem with this is that the visibility of the pair is so different in different parts of the world, different times of the year/night and, most importantly, during different weather. I guess in places where you get the same kind of clear nights many times it would be a good test.
And since the test never changes, it's easy to give the expected answer.
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  #8  
Old 25 February 2007, 03:21 PM
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Brad from Georgia Brad from Georgia is offline
 
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I understand that in recent years, a better test of eyesight is to watch for Britney's panties when she's getting in or out of a car.
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  #9  
Old 25 February 2007, 09:58 PM
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Silas Sparkhammer Silas Sparkhammer is offline
 
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I understand that in recent years, a better test of eyesight is to watch for Britney's panties when she's getting in or out of a car.
Drink, hell: I owe you an entire bar!

Silas
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  #10  
Old 25 February 2007, 11:36 PM
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Hero_Mike Hero_Mike is offline
 
 
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Originally Posted by Brad from Georgia View Post
I understand that in recent years, a better test of eyesight is to watch for Britney's panties when she's getting in or out of a car.
That's not a test for eyesight, it's a test for dementia.

Because if you're seeing things that aren't there, then you're really not "all there" yourself....
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