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Equipment Discussions >> Cats & Casses

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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: CO vs. All That "Other Stuff"! new [Re: DesertRat]
      #5622768 - 01/14/13 02:15 PM

Quote:

hopefully its clear now to others the different ways to view aberrations




What's clear is how complex the subject is, and how much I have to learn!


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Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: CO vs. All That "Other Stuff"! new [Re: Joe Cepleur]
      #5622840 - 01/14/13 03:02 PM

The eye even more so, that would make for some great debate: scale, illuminance, resolution, photopic through scotopic vision, etc. The eye can perceive color, the MTF doesn't treat color very well. What I mean is, once you learn to discern subtle color differences on Jupiter, so much more resolution is open to you, for example, than simple sinusoidal contrast transfer. This very thing occurred to me recently, and now I see Jupiter in low saturation but very distinct hues. Its amazing to distinguish not just brown from white, but varying tones of gray from each other, white from Tawney, blue from ruddy, etc. Here, brightness and image scale play a role as well as contrast.

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Alph
Carpal Tunnel


Reged: 11/23/06

Loc: Melmac
Re: CO vs. All That "Other Stuff"! new [Re: DesertRat]
      #5623089 - 01/14/13 05:13 PM Attachment (4 downloads)

Quote:

A blown up MTF shown here indicates some real added contrast at the Rayleigh line for these high spatial frequencies. Actually seeing it and proving the case is another matter.



From your graph, the MTF is no greater than 0.02 at the Dawes limit.
I have created a simple graph using sagemath to depict in red what is left from the original signal at the Dawes limit. The sage command is
(sin(x)).plot(xmin=0,xmax=20*pi)+ (0.02*sin(x)).plot(xmin=0,xmax=20*pi, rgbcolor=Color('red'))


Edited by Alph (01/14/13 07:25 PM)


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DesertRat
Post Laureate
*****

Reged: 06/18/06

Loc: Valley of the Sun
Re: CO vs. All That "Other Stuff"! new [Re: Alph]
      #5623157 - 01/14/13 05:56 PM

Alph,

Interesting, but as you see in your quote that I referred to Rayleigh, not Dawes. Even so recording or measuring there would be a delicate operation.

Glenn


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Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: CO vs. All That "Other Stuff"! new [Re: DesertRat]
      #5623708 - 01/15/13 12:42 AM

Again, Alph, that graph occurs at a higher spacial frequency than for unobstructed apertures.

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