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Thread: 1.25" vs 2"

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    Default 1.25" vs 2"



    Is there any benefit to a 2" eyepiece over a 1.25"? What are the pros and cons of each?

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    Default

    You don't even need to search - just scroll down and look at the thread titles in this sub-forum.

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    From my archive:

    The advantages of a 2" light train are not necessarily great in some ways. Its going to come down to the types of EP's that you may plan to use and the focal length of your scope.

    In general using standard Plossl type EPs there is absolutely no advantage in 2" until you go to EPs of 32mm or longer focal length. Incidentally if you have a scope of very short focal ratio, say f/4 or less, then standard plossls aren't going to work particularly well at all in any case.

    The actual switch to 2" does have an advantage with EPs with wider than standard Plossl AFOV

    Examples are:

    If you want to use 100░ AFOV EPs then 17mm or longer will need to be 2" for maximum advantage, at 82░AFOV it is 20mm and at 68░AFOV 27mm will be the magic number.

    You may also note that a 100░ AFOV EP is probably going to cost you more than your next scope

    From my personal perspective, however, there is a very strong case for the reason that I only use 2" focusers, diagonals, and barlows (ie 2" light trains) and that is my preferred EPs are very physically large and heavy. In a 2" system large and heavy EPs are much better mechanically supported than in a 1.25" system despite there being no actually gain over 1.25" in actual view in the shorter EP lengths.

    Similarly from an AP perspective a 2" focuser offers much better mechanical support for a camera than does a 1.25"

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    Quote Originally Posted by Vinnie View Post
    From my archive:
    You may also note that a 100░ AFOV EP is probably going to cost you more than your next scope
    Yeah, I'm seeing this! I was impressed with the reviews of the Tele Vue Ethos line, but they're around $600. Hmm...

    So am I to understand that if you get the wide AFOV EPs in longer focal lengths, eventually it clocks over to 2"? Similarly, as you move to narrower views and shorter focal lengths you're in the 1.25" range?

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    So am I to understand that if you get the wide AFOV EPs in longer focal lengths, eventually it clocks over to 2"? Similarly, as you move to narrower views and shorter focal lengths you're in the 1.25" range?
    Never thought of it that way but that would be correct

 

 

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