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  1. #1
    redjmp's Avatar
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    Default ED 2" for Celestron 80ED



    I am thinking of getting into 2" ep's for my new scope.
    But I am an astronomy newbie and really don't have a clue why or what to get lol!
    I currently have it setup with a 1.25 45 erecting prism with a 25 plossl and a 15wa & 2x barlow from antares.
    What would be the advantage of going with a 2" ep?
    Is there much difference with an ED over a standard?
    Currently I get almost as much spherical aberation as with my 90mm f11/1000
    What sizes should I get for this scope?(80mm f7.5/600)
    Is there a 2' binoveiwer available at a reasonable price3 and if so what size ep's are recomended for it?
    Or should I stick with a standard binoviewer?

    Thanks y'all!

  2. #2
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    Default

    Welcome to the forum. The lower magnification 2" eps will give you wider field when looking through them. On the higher mags I don't think it helps as much. You will also have to buy a 2" diagonal if you go that route. Also, 45 degree diagonal will give off a darker view than a 90 degree. I use 2" eps and love them. For me they are easier to look through. Obviously that is subjective. Someone should be along shortly with a better explanation of the differences between the two. Cheers.
    name: Derek

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    and such.

  3. #3
    redjmp's Avatar
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    Default

    OK then. I can't really seem to find any higher power 2" than about 15mm so I guess thats why.

    So to be clear adding a 2" diagonal wont help in getting more light through the eyepiece.
    I will still have the same dim view as with a 1 1/4" at medium and higher mags?

    So at what size ep will a 1 1/4 diagonal show its limitations?
    And when it does, will things get dimmer or will it start to have tunnel vision?

    As well, do I need to go with ED or lanthanum ep's to be free of spherical aberation?

    Or will all good quality ep offer colour free views?

    Any ep recommendations for my ED 80?
    Howabout for my soon to arrive Byers C8?
    It does not have a diagonal so would a 2" be a good choice or will the long focal length negate the benefits of going larger than the 1 1/4"diagonal?

    I was thinking of maybe getting the Celestron 2" kit as it has a diagonal that looks like it can work with both my 80ed and c8 but I have never seen a c8 up close yet so I am not sure what I need. I think it has a visual back? Do I need this for a 2" diagonal?

    Am I going to get much better performance using a really expensive televue over those celestron ep's on my c8 or are those really expensive panoptic and ethos's designed for really fast scopes?

  4. #4
    Lenbo's Avatar
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    Default

    Hi redjmp. There are some great writeups in the stickys at the top of this forum. They explain the benefits of 2" versus 1 1/4" in relation to focal lengths of the scope as well as the impact on pupil size. All factors that influence eyepiece performance in your scope. These guys did a pretty good job explaining these concepts in a fairly easy to follow manner.
    Len
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  5. #5
    carnevali's Avatar
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    Default

    Hello, and welcome. I don't have answers to your questions, but can perhaps offer a little bit of preliminary experience I've had with some EP. I've tried my new 2" Baader diagonal and I love it. The only 2" EP I have are 30 mm and 38 mm, although I just ordered a 26 mm Q70 and am eyeing a 17 mm Televue Nagler (expensive, but, oh what a nice birthday present it will make!). Shorter focal lengths don't seem to be available, really, but the wide field, open views you get with the longer focal lengths are truly beautiful. I tried them on my 115 mm refractor (f=890 mm) and 80 mm refractor (f=600 mm). They worked well on both. I also quickly tested the FOV of the 2" Zhumell 30 mm vs the 1.25" bright-light Plossl 32 mm on a terrestrial target. The 2" EP had a definitely larger field of view, but it was surprisingly slightly less bright than the 1.25" EP. The Q70 38 mm EP had a much larger FOV and it was as bright as the 30 mm. All in all, I do like the 2" EP views in my refractors (and I also use them in my 10" Dob). The Moon, for instance, looks glorious in them, as well as the Beehive, Double cluster, M81 & M82 and other large size objects.

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    Antonino Carnevali

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  6. #6
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    Default

    Oops, sorry, I should have read my notes: the 2" 30-mm and 38-mm were less sharp (not less bright) than the 1.25" 32-mm EP.

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    Antonino Carnevali

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