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Re: Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
From: Frank Reed CT
Date: 2005 Feb 12, 23:41 EST
From: Frank Reed CT
Date: 2005 Feb 12, 23:41 EST
Alex you wrote:
"On your earlier message today on the human eye resolution.
I think it is more complicated than that.
"Resolution" is the ability to see two point sources apart.
But frequently I see two stars collided in one spot, (so I already cannot
tell them apart) but still understand
that this collision is not perfect. Then I try to make this "spot"
as small as I can. I believe that a human eye can be trained to increase
this ability."
I think it is more complicated than that.
"Resolution" is the ability to see two point sources apart.
But frequently I see two stars collided in one spot, (so I already cannot
tell them apart) but still understand
that this collision is not perfect. Then I try to make this "spot"
as small as I can. I believe that a human eye can be trained to increase
this ability."
Yes, there is definitely one step that you can go beyond the standard
optics definition of resolution. And yet, I do find that the extra magnification
is just what's required based on roughly 1.5 minute unaided resolution to
get to 0.2 minute accuracy based on the standard definition. One example
of a visual skill that's a step beyond resolution (that we've
discussed before) is the ability to bring two large circles, like the images of
the Sun and the Moon, into perfect tangency. There is still a resolution
issue here, since you have to resolve the edge to define it, but the amazing
thing is that we can do a pretty good job estimating when two circles would be
in perfect tangency even if the actual point of contact is hidden from view. So
you're right that there is definitely a larger perception issue at work
here.
And you wrote:
"If you look at the marksmen results (with a rifle, with no optical
sight)
you can conclude that the human eye ability to aim a rifle is
better than 1'."
you can conclude that the human eye ability to aim a rifle is
better than 1'."
Interesting. I don't know anything about this. What can a typical trained
marksman achieve in terms of angular accuracy? While I'm thinking of
it, do we know if there are any people who have genetically superior foveas
in their eyes with the cones more tighly packed to achieve superior
resolution --and superior marksmanship?
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars