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Thread: Wide-Field Eyepiece - Same Magnification?

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    Default Wide-Field Eyepiece - Same Magnification?



    Now, I have done some research into this before deciding to post this question, but the jury seems to be out.

    Does a 10mm 82° eyepiece provide the same magnification as a 10mm 52° eyepiece?

    Just to clarify matters - If Jupiter is the size of a penny in one, will it be the size of a penny in the other?

    Many thanks.
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    Default Re: Wide-Field Eyepiece - Same Magnification?

    As far as I know, so long as the scope is the same, the magnification results will be the same and the size of the target will be the same. The main difference would be the true field of view (TFOV) in the eyepiece, 0.4-degrees for the 52-degree eyepiece and 0.7-degrees for the 82-degree eyepiece.

    However, there is an optical illusion that causes identical-sized objects to look different, depending on what's surrounding them. This can play tricks on the mind's perception. Below is an example - the circles in the middle are identical in size, but one appears to be smaller than the other. In some circumstances, with more real estate surrounding an object in the eyepiece, it may seem smaller.

    optical illusion.jpg

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    Default Re: Wide-Field Eyepiece - Same Magnification?

    It will be the same size. You'll just have more space around Jupiter in a 82° eyepiece. For a manual scope (no goto), the advantage would be that Jupiter stays in the field of view longer, so I wouldn't have to move it as often. For a goto scope, as far as planets go, there isn't really much of an advantage to a wide eyepiece.
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    Default Re: Wide-Field Eyepiece - Same Magnification?

    Physically - yes. But to your eye (or to my eye at least ) Jupiter appears bigger in 60 vs 82 degree EP, but as other stated it is just an illusion.

    If you have a tracking mount you would appreciate using 50 degree EP more (giving that it is of the same optical quality as 82 degree), because it will be easier for your eye to stay focused on the planet.

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    Default Re: Wide-Field Eyepiece - Same Magnification?

    Quote Originally Posted by rogercorbett View Post
    Now, I have done some research into this before deciding to post this question, but the jury seems to be out.

    Does a 10mm 82° eyepiece provide the same magnification as a 10mm 52° eyepiece?

    Just to clarify matters - If Jupiter is the size of a penny in one, will it be the size of a penny in the other?

    Many thanks.
    Unequivocally, yes. That's what "same magnification" means. Magnification is a function of the eyepiece focal length and the OTA focal length.
    Last edited by KathyNS; 05-16-2016 at 07:57 PM.

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    Default Re: Wide-Field Eyepiece - Same Magnification?

    Quote Originally Posted by Bigzmey View Post
    Physically - yes. But to your eye (or to my eye at least ) Jupiter appears bigger in 60 vs 82 degree EP, but as other stated it is just an illusion.

    If you have a tracking mount you would appreciate using 50 degree EP more (giving that it is of the same optical quality as 82 degree), because it will be easier for your eye to stay focused on the planet.
    All makes perfect sense. I have a tracking mount and two 82° eyepieces, a 10mm and a 31mm. I get your point about the 50° eyepiece, but I'm working on the Astronomy League no GOTO Messier program and I like being able to look around within the eyepiece. Also paired with my scope, the FOVs quite closely match up with the inner rings of a Telrad.
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    Default Re: Wide-Field Eyepiece - Same Magnification?

    i think this image describe it better than words

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    Default Re: Wide-Field Eyepiece - Same Magnification?

    Quote Originally Posted by rogercorbett View Post
    All makes perfect sense. I have a tracking mount and two 82° eyepieces, a 10mm and a 31mm. I get your point about the 50° eyepiece, but I'm working on the Astronomy League no GOTO Messier program and I like being able to look around within the eyepiece. Also paired with my scope, the FOVs quite closely match up with the inner rings of a Telrad.
    For DSOs it is the other way around. I prefer wide EPs, at least 68 degrees. I find that DSOs stand out better if they are framed nicely with plenty of room around.
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    Default Re: Wide-Field Eyepiece - Same Magnification?

    Another positive about the wider fov eyepieces is that they allow you to use higher magnification on some larger objects.

    For example, to get my max fov I can use a 32mm plossl or I can use a 24mm 68 degree eyepiece. Both will give me my max fov, but the 24mm will give me a darker sky background which often makes for a better view.
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    Default Re: Wide-Field Eyepiece - Same Magnification?

    The greater degree EP (give same mag) allows you to see the target in context, for example I like to view Jupiter along with it moons. But each to their own pleasure.

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