NavList:

   

Reply

I thought of one other example for the case of magnification and the 
constantcy of "intensity" (which in this case is the apparent "surface 
brightness" of a celestial object). Consider how we select shades for viewing 
the Sun through a sextant. I'm sure most of us do the same thing... You hold 
up the sextant towards the Sun's with the shades swung out of the normal 
optical path and then starting with the darker shades, you experiment with 
combinations until you get a comfortable low-intensity image. Then you swing 
those shades into the optical path between the mirrors and look through the 
telescope at the Sun. Even with a relatively high magnification scope at 7x, 
the image of the Sun is every bit as "comfortable" to look at as it is when 
the shades were being used "naked eye" while swung out of the optical path. 
The image of the Sun has the same intensity of light across the disk --it is 
only increased in total angular diameter. The telescope does not increase the 
amount of energy or the brightness of the light on the fovea. It increases 
the TOTAL amount of light entering the eye over a large area.

-FER



--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply