Re: Expensive Small Aperture Refractor?

tony_flanders@xxxxxxxxx wrote: 
Shneor wrote:


Visually speaking, small, high quality refractors are great if you
don't mind not being able to view 80% of what you can see ...
with an 18".



Actually, I compute that as closer to 99%.

An 18" scope has 4.5x the aperture of a 4" scope, gathering 20.25x
as much light, and allowing you to see equivalent objects 4.5x
farther away. So for any given absolute magnitude of star or DSO,
the 18" scope covers 4.5^3 = 91x times the volume. In other words,
only one out of every 91 stars or objects visible in the 18" is
visible in the 4" scope.


Doesn't that make it 1.1%???
.

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