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Thread: 1.25" vs 2" EPs at low focal lengths

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    Default 1.25" vs 2" EPs at low focal lengths



    I read somewhere (cant remember where) that at low focal lengths, say 12mm and below, its not really worth getting expensive 2" EPs because there really isnt much difference compared to good 1.25" EPs. Is this true, or even at low focal lengths do 2" EPs really shine (wider AFOV, larger lens radius to look through)?

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    Hey, Joe.. Welcome. I think that's right, but I am not sure. I only have a 1.25 focuser, so haven't needed to do such research myself.
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    All of my higher powered eyepieces (those under 25 mm) are 1.25 inch eyepieces and all of my lower powered eyepieces (those 26 mm and above) are 2" eyepieces...

    below 25 mm a 2" eyepiece gives you NOTHING..
    above 26 mm the field stops are bigger in 2" eyepieces therefor your get a larger FOV ...

    You DO NOT NEED a wide field of view when boring deep inside a crater on the moon nor to view planetary detail but you sure like as large a FOV as possible when trying to frame a DSO ...

    Heck does anyone really sell a 2" High Powered eyepiece...????

    To get a larger "Peep hole" to look thru with high powered eyepieces buy an eyepiece with more eye relief...


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    Retired, also have 2 other hobbies
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    There is a theoretical minimum magnification for every scope, but personal experience tells me it can be (slightly) exceeded. It has to do with the exit pupil getting too big. When using my 35mm Siebert, I must be sitting down to be able to hold my eye in the "sweet spot".
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    Thank you both, this clears it up for me!

    Though Ive always wondered... doesnt more eye relief narrow the FOV even more as you are farther away from the lens (what is the lens that one looks through called?)?

    BTW, I didnt even realize high power EPs didnt come in 2"! Thanks for putting up with my ignorant first couple of posts.

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    Quote Originally Posted by JoeThePro View Post
    Thank you both, this clears it up for me!

    Though Ive always wondered... doesnt more eye relief narrow the FOV even more as you are farther away from the lens (what is the lens that one looks through called?)?
    More eye relief normally makes it easier to find the center of the eyepiece to look through, and it is important to people who need to wear glasses, as they cannot get as close to the eyepiece.

    A word of caution, some long eye relief - wide angle eyepieces can soften or wash out fine detail, also, some of them require a person to look almost directly in the center of the eyepiece to see anything. People new to telescopes have the most problem with them. This is an example of the lens that produce these problems: Orion Epic ED-2 Telescope Eyepieces | Orion Telescopes

    As to the second half of your question, you are talking about an eyepiece.

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    Quote Originally Posted by swing848 View Post
    More eye relief normally makes it easier to find the center of the eyepiece to look through, and it is important to people who need to wear glasses, as they cannot get as close to the eyepiece.

    A word of caution, some long eye relief - wide angle eyepieces can soften or wash out fine detail, also, some of them require a person to look almost directly in the center of the eyepiece to see anything. People new to telescopes have the most problem with them. This is an example of the lens that produce these problems: Orion Epic ED-2 Telescope Eyepieces | Orion Telescopes

    As to the second half of your question, you are talking about an eyepiece.
    I would assume the problems you mentioned are only for less expensive wide angle pieces... I cant imagine a ultra wide 5000 or nagler washing out fine detail....??

    And I know its called an eyepiece!!! I meant the actual glass in the front. Isnt there a specific name for that area?

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    Quote Originally Posted by JoeThePro View Post
    .......... I meant the actual glass in the front. Isnt there a specific name for that area?
    Yeah, I always wondered that myself. I know the big end is called the Objective, maybe the small end is the Subjective.
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    Quote Originally Posted by JoeThePro View Post
    I would assume the problems you mentioned are only for less expensive wide angle pieces... I cant imagine a ultra wide 5000 or nagler washing out fine detail....??

    And I know its called an eyepiece!!! I meant the actual glass in the front. Isn't there a specific name for that area?
    I apologize for my error. The piece of glass in an eyepiece closest to your eye is called the "eye lens".

    As to expensive long focal length, wide angle eyepieces, they are inferior to many less expensive eyepieces, including, in some cases, those made by University Optics. Now, I must qualify this statement by mentioning that, if you have a fine telescope, different eyepieces will provide better or worse seeing depending upon the type of telescope.

    In other words, specific eyepiece designs are needed if you want the best view from your telescope, especially if you are a seasoned astronomer and have good equipment.

    Although narrow in scope, this link may help you concerning my comment: Astromart Reviews - The Good, The Bad and The Ugly: Televue Nagler 31mm Type 5, University Optics 32mm König Mk-80 and Meade 30mm QX Wide Angle Three Way Eyepiece Shootout.

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    I was not going to add this, however, the question may arise, so, I should probably add it.

    In an eyepiece, the glass that is furthest from the eye is called the "field lens".

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