Diffraction rings

From: Steve Maddison (steve_at_cosam.org)
Date: 11/28/04 

Date: Mon, 29 Nov 2004 00:18:00 +0100

Hi all,

I've been reading up on optical theory, but can't seem to find any
answers to a query or two I have about diffraction rings.

I've had a Meade LX90 for several months, but to this day never seen any
hint of diffraction rings around the Airy disk of any stars, regardless
of brightness. I never thought anything of it, but I recently got my
hands on an Orion 80mm ED refractor, and in this scope the rings are
obvious, epecially at powers above 100x.

I'm trying to get the reason for this straight. From what I've read, I'd
expect the rings to be more obvious in the LX90, due to the central
obstruction, whilst the opposite is true. I'm curious as to which
factors affect the diffraction pattern of a scope. I can imagine things
like the quality of the optics and collimation have something to do with
it, but can't seem to work out how this all fits together.

Whether or not such rings are visibile doesn't bother me too much - I
find a nice, sharp, ringless disk pleasing enough, although a disk with
rings also has a certain beauty to it. Is there an ideal or prefered
situation?

Any, even partial, explanation would be most appreciated, as would a
link to a web site which covers such topics in detail.

Thanks in advance, and clear skies to you,

  Steve 

-- 
Steve Maddison
Den Haag, The Netherlands
http://www.cosam.org/

Relevant Pages

  • Re: Diffraction rings
    ... With the larger scope you want better ... seeing to push it up against the limits of diffraction. ... not see rings in that scope. ... > hint of diffraction rings around the Airy disk of any stars, ...
    (sci.astro.amateur)
  • Re: Diffraction rings
    ... >Steve Maddison wrote in message ... ... >>answers to a query or two I have about diffraction rings. ... then look for a clean Airy disk. ...
    (sci.astro.amateur)
  • Re: Refractors, Diffraction Rings?
    ... >>> Those are not diffraction rings. ... Airy disk in an in-focus point source is also as commonly described by ... SAA can be pretty confusing in and of itself sometimes... ...
    (sci.astro.amateur)
  • Re: More on diffraction rings
    ... rings we see around stars, and should never be called the same thing. ... The diffraction pattern you see in the eyepiece ... is just a slice of a three-dimensional pattern. ... Personally, I prefer to call them in-focus diffraction rings, in order ...
    (sci.astro.amateur)
  • Re: Scope Mounts on a Springfield 1903A3
    ... If the existing bases and rings are doing their job, ... certainly more complicated and expensive mounts exist than the Weaver. ... compensate for in the alignment of the scope tube with the barrel. ... they will not "fit" their rifles or that making them fit requires ...
    (rec.guns)
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