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Thread: Differences between 1.25 and 2" eyepieces

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    Post Differences between 1.25 and 2" eyepieces



    I am new to astronomy and have just purchased a new telescope that fits both 1.25 and 2" eyepieces i was Just wondering if there is any differences between the two sizes, if so is it worth investing in both sizes and what are people's personal opinions on the different sizes

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    Default Re: Differences between 1.25 and 2" eyepieces

    2" eyepieces are for wide field low power views so are typically 28mm and larger. Use 1.25" eyepieces for higher magnification but eye relief can be a factor at less than 10mm.
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    Default Re: Differences between 1.25 and 2" eyepieces

    Generally you won't find the same eyepiece in two different sizes. For example in the ES 82° eyepiece series the 30,24 and 18mm eyepieces are 2" eyepieces while the 14, 11, 8.8mm are 1.25" eyepieces since they have smaller fields of view and don't need the extra width in the light path that the longer focal length eyepieces do. The good thing is since your scope can use either you can just pick the eyepiece that fits your needs and use it without worrying if it's 1.25 or 2".
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    Default Re: Differences between 1.25 and 2" eyepieces

    Welcome to the forum.

    The difference is just in the width of the field of view. Long focal length wide angle eyepieces need the extra width of the 2" barrel to accommodate the FOV. Shorter focal length high magnification eyepieces don't, and it is cheaper to make them in the 1.25" size.
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    Default Re: Differences between 1.25 and 2" eyepieces

    i like 2" for FOV as i find it less strain on my eyes , specially as i dont wear either my glasses or contacts when viewing, i have one currently set for 2" and 1 for 1.25" and i find that using the 1.25" on the 2" diagonal i dont get the same amounts of light
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    Default Re: Differences between 1.25 and 2" eyepieces

    Quote Originally Posted by Woody94 View Post
    I am new to astronomy and have just purchased a new telescope that fits both 1.25 and 2" eyepieces i was Just wondering if there is any differences between the two sizes, if so is it worth investing in both sizes and what are people's personal opinions on the different sizes
    If there were no differences the manufacturers would only have 1 eye-piece size (and I wish it was 2"). In shorter focal lengths (around 20mm and on down to around 4mm) EP's the 1.25" format work fine and are less costly to manufacture and purchase than their 2" brethren, if you can find them.

    The problem for me is the stupid adapter. I can affect collimation if removed and replaced. It is a hassle in the dark when changing formats. If dropped it can be difficult to find in the dark. For me a PITA.

    All of my EP's are set up for 2" format, either they have barrels machined for both formats, or I buy a 2" adapter (Adapter), remove the thumb screw and replace it with a set screw to make the 1.25" EP a 2". This does negate the cost savings of a 1.25" EP but for me well worth the money with the reduction of the hassle factor.

    A 2" format is required for wide field EP's ( 68° or greater) in longer focal lengths (around 20mm and upwards to and beyond 40mm) due to the size of the field stop. In some cases the barrel of the EP is actually the field stop.

    JJ
    Telescopes: Assorted brands and designs from 60mm up to 203mm (9). Eyepieces: Two 6mm BO's (Brown Organics - Eye Balls). Mounts: Celestron, Meade, Orion, Vixen, Skywatcher. Cameras: Canons, Logitech, Orion, QHYs.

 

 

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