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    Nodgiles's Avatar
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    Default Resolution vs resolving power



    Can anyone explain the difference of these two specifications and what they mean? Ive done some digging on sights and everything is very technical and a bit over my head. I understand that the resolving power is the ability to split stars but how does this differ from resolution? Everything I read references one as the other in some fashion but its in a language I dont speak very well (mathmatics)

    For instance the resolution of my scope is 0.92 arc seconds and the resolving power is 0.77

    Im just not able to wrap my head about the differences and what they mean. . .
    Leith
    Celestron C6-A | GoTo HEQ5 | Baader Hyperion 13mm, 21mm | Canon Digital Rebel XS

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    Don't think we've forgotten you Leith. I am searching heaps of resources here to see if I can find something simple enough for us both to understand.

    Generally these are not numbers that I get terribly concerned about. I know which scopes I have that can split tight doubles when the sky lets me, and which aren't so good at it so I usually just accept that!

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    Here is something without any mathematics involved.
    Resolving power is the ability of the components of an imaging device to measure the angular separation of the points in an object. The term resolution or minimum resolvable distance is the minimum distance between distinguishable objects in an image, although the term is loosely used by many users of microscopes and telescopes to describe resolving power.

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    Quote Originally Posted by star drop View Post
    Here is something without any mathematics involved.
    Resolving power is the ability of the components of an imaging device to measure the angular separation of the points in an object. The term resolution or minimum resolvable distance is the minimum distance between distinguishable objects in an image, although the term is loosely used by many users of microscopes and telescopes to describe resolving power.
    By your definition. . .

    resolving power = ability to measure the angular separation of points
    resolution = minimum distance between distinguishable objects in an image.

    Now I may be way of base, but both of these still sound like splitting stars to me. There must be more to it as my scope has different resolving powers and resolution.
    Leith
    Celestron C6-A | GoTo HEQ5 | Baader Hyperion 13mm, 21mm | Canon Digital Rebel XS

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    Aren't these just two different forms of the same word?

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    Default

    one might think, however my scope has different values for each. The resolution of my scope is 0.92 arc seconds and the resolving power is 0.77
    Leith
    Celestron C6-A | GoTo HEQ5 | Baader Hyperion 13mm, 21mm | Canon Digital Rebel XS

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    Yeah well that's the bit I don't get

    The resolution in arc seconds is a direct function of aperture, and is relevant to separating single objects from each other. Incidentally it is often said that better than 1.0 arc seconds is hard to achieve in reality because of atmospherics, but it certainly can be done.

    The second number suggests something based on wave fronts, but I really don't know.

    Incidentally there are different formulae for determining resolution that come up with different numbers. Dawes Limit is one, but there are three of four others, and to be honest the maths involved is gibberish to me.

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    Quote Originally Posted by Gandalf223 View Post
    Aren't these just two different forms of the same word?
    Yeah well that's how I always thought of it, Alan, but well

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    Okay guys here's one that I can follow, but you will see that the figures vary a lot depending on which limit is applied

    the astroscopic labs - article: The Resolution of a Telescope - Dawes, Rayleigh and Sparrow

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    Eureka!

    Well I think so anyhow..........

    Leith the 0.92 arc seconds corresponds to the Raleigh Limit for your scope, and the 0.77 arc seconds corresponds to the Dawes Limit for the same scope. So if you read the link above you will see that these are two different applied methods which use a different standard to try to define what comes down ultimately to much the same thing.

    I guess that one distributor prefers to quote Dawes, and another prefers to quote Raleigh?

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