Re: Building 30" Drum Scope
- From: Hayden <haydenfleming@xxxxxxxxx>
- Date: Sat, 30 May 2009 07:19:13 -0700 (PDT)
On May 30, 9:39 pm, Chris L Peterson <c...@xxxxxxxxxxxxxxxxxx> wrote:
On Sat, 30 May 2009 01:41:22 -0700 (PDT), Hayden
<haydenflem...@xxxxxxxxx> wrote:
I can't believe why you mention that without an objective,
the focal plane is at infinity.
You are confusing a pinhole imaging system with an aperture producing a
diffraction pattern. They are completely different things. When you are
simply producing a diffraction pattern, the aperture is illuminated with
a plane wave and there is no image. If you have a complex wave front,
you can consider an aperture to be a pinhole lens, with an image formed
geometrically at infinity, although you don't have to go that far to
reach the resolution limit created by diffraction.
_________________________________________________
Chris L Peterson
Cloudbait Observatoryhttp://www.cloudbait.com
But one can consider a complex wave front as composing of
a plane wave that directly comes on-axis with another
plane wave at an angle that is closest to the on-axis plane
wave. And the diffraction created in those plane waves
can produce an image just like in an aperture with lens.
Ins't it? Also when you said an image formed geometrically
at infinity in complex wavefront. Are you speaking of the
image being formed from the shadows of the aperture like
in pinhole or as image formed with diffraction discs as in a
lens or objective based image system? .
Hay
.
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