From: noelturntive@live.co.uk   
      
   On Thursday, 2 November 2023 at 16:33:24 UTC, Phil Hobbs wrote:   
   > Lou  wrote:    
   > > I am short sighted so anything at arms length or beyond is *completely*   
   out of focus.    
   > > Just noticed though that if I hold a pair of reading glasses ( not mine    
   > > as I don’t need them for close up vision) at arms length the frame and    
   > > everything around is out of focus as usual but the image coming through    
   > > the lens of the background scene is in complete 20:20 sharp focus .Albeit   
   upside down.    
   > > Cant quite figure out how this works. Is it something to do with the    
   > > focal length in my eye between the lens and retina?    
   > >   
   > You‘ve invented the telescope. ;)    
   >    
   > The reading glasses are forming a real image (aka an aerial image) between    
   > them and your eyes. Because the glasses’ focal length is short, the image    
   > is far enough away that you can focus on it.    
   >    
   > If you draw a ray diagram, you will see why the image is rotated 180    
   > degrees—inverting in both x and y directions is equivalent to a half turn.    
   >    
   > Cheers    
   >    
   > Phil Hobbs    
   >    
   > --    
   > Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /    
   > Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics   
      
   Here’s another odd effect that maybe you can shine a light on.   
   I don’t know if you’ve noticed this effect, it’s probably not that good   
   for my eyes.   
   If I look a the reflection of the sun off of a kitchen ornament which is   
   essentially   
   a circular strip of reflective metal I see a hilite of the reflected sun.   
   Around it I see an aura that looks a lot like those images of magnetic fields    
   on iron filings.   
    https://en.wikipedia.org/wiki/Magnetic_field#/media/File:Magnet0873.png   
      
    I presume the ”aura” is something to do with the light being    
   dispersed by the material of the retina or maybe the fluid in the optical   
   cavity.   
      
   Anyways to cut a long story short if I rotate my head the magnetic field   
   image in the aura doesn’t rotate. It’s always at the same angle relative   
   to the   
   reflection. And thus relative to the sun.   
   Am I seeing the angle of polarisation of the suns reflected light after its   
   been   
   Plane polarised by the reflection? Kind of like an optical version of   
   a calcite crystal used by the vikings.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)