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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
From: Bill B
Date: 2005 Feb 22, 23:59 -0500
From: Bill B
Date: 2005 Feb 22, 23:59 -0500
Alex stated: > "Yes. > I think some misunderstanding comes > from your implicit assumption that the > eye > is an "optical system":-). > Several participants of this discussion mentioned a > conjecture that the eye resolution higher than optical > limit might be due to the eye micro MOTION. > If you take this motion into account, the eye cannot > be considered > a purely optical system anymore.> Frank," Well put Alex. Playing the devil's advocate, an extremely sophisticated optical system. Somehow the discussion has remained focused primarily on the eye, not the system; which includes the brain. The eye is a receptor(s). The brain--and cross-talk mechanisms perhaps in the eye--provide the software to interpret the signals. And amazing software it is (both the receptors and the brain). Also, the color receptors of the eye do not act independently. They do cross-talk, modifying the information from the individual receptors. Or so says CIE propaganda ;-) Bill > >> Imaging resolution in any >> optrical system is ultimately limited by diffraction > > Yes. > I think some misunderstanding comes > from your implicit assumption that the > eye > is an "optical system":-). > > Several participants of this discussion mentioned a > conjecture that the eye resolution higher than optical > limit might be due to the eye micro MOTION. > > If you take this motion into account, the eye cannot > be considered > a purely optical system anymore. > > Of course this is only a conjecture, but this is what I had > in mind when I said that this unusually high resolution > does not contradict yet the laws of physics. > > > Put in other words, I can easily imagine a mechanism > which achieves high resolution using an optical system > of low resolution. > > Let me also define what I mean by resolution: > It is the ability to decide whether the images of two > points coincide. You don't necessarily have to SEE them as > separate points when they dont coincide for this. > > For example, in the shooter's case, this is the ability > to decide whether the bullet trajectory will pass through > the center of the target, though she does not necessarily > see the center of the target, even less the bullet trajectory. > > In the case of measuring star distances with a sextant, > I can see two stars as one dot, but still understand that > this dot is somehow "imperfect". > This really happens when the distance > is about 0.5' (with my scope). > But still I somehow can measure > to 0.1' in many cases. > Alex.