Re: [ATM] Betr.: 48" Dob at OMI

[Andy Saulietis <iss@pvtnetworks.net>]

Hello Alexis,

Another way to look at the apparent brightness of extended objects 
thru a telescope
is using the concept of 'normal' magnification, which is simply the 
magnification you
get when the telecope's exit pupil is about 7mm, or 4x the telescope 
aperture in inches.
The view one sees (neglecting transmission losses) at this 
magnification is the same as if you moved your eye closer to
the object by the amount of that magnification. Point sources such as 
stars would appear brighter by the
square of the magnification, but extended objects would not get 
brighter per unit area. They would just
increase in apparent size. The total energy in the image would 
increase just the same as that for a star.

Andy Saulietis
Former NASA optical visibility guru <g>


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