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  1. #1
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    Default Cost aside...Why not all 2" EP's?



    Just wondering is there any reason other than cost that a beginer like myself just wouldn't want to go with all 2" over 1 1/4 EP's?

    my scope will be able to handle them one i change the Diagonal.

    Just wondering.

  2. #2
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    Default

    Cost first and foremost, cost/benefit secondarily...

    If you survey the broad market, 2" eyepieces in short focal lengths (less than 20mm) become hard to find, prohibitively expensive, and of marginal optical benefit in high-magnification application.
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  4. #3
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    Weight is another issue.
    Many people own small setups that could easily be unbalanced by great big 2" EPs.
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    Default

    I would ask why would you want too? If you look at the size of the beam it is unlikely you can take advantage of a 2 inch lens unless you have a very large scope.

    I have an LX90-8. The secondary is only 2 inches. Certainly I won't see any image large enough to need a 2 inch ep.

    A friend has a 12 inch LightBridge. At very low magnification he does have a need for a 2 inch to get the widest possible FOV. At higher magnification the FOV is determined by the apparent FOV divided by the magnification. For a FOV of about 1 or 2 degrees, you can't get a beam larger than the 1.25 inch except with large scopes.

    Another friend has a 22 inch dob. He can and does use 2 inch eps.

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    I would ask why would you want too?
    I don't know if i want too, but i really didn't know what specific questions to ask so i just asked a very general question. (I'm a new to this and just trying to figure stuff out.)

    If you look at the size of the beam it is unlikely you can take advantage of a 2 inch lens unless you have a very large scope.
    At higher magnification the FOV is determined by the apparent FOV divided by the magnification. For a FOV of about 1 or 2 degrees, you can't get a beam larger than the 1.25 inch except with large scopes.
    FOV=AFOV/MAG = beam size?

    What size Refractor would you need to take advantage of 2" EP"s and also is this true for the diaganol also?

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    Quote Originally Posted by kencrowder View Post
    I would ask why would you want too?
    Let see... Easier to handle, especially with gloves on, consistancy with my other eyepieces (I use all 2"), consistancy with all my imaging gear (again, all 2"), consistancy with my filters (again, all 2"), nice wide place to rest my brow, more stability, less likely to poke me in the eye like a sharp stick :-)

    Hey, to each their own, I like having all 2" compatible eyepieces etc.

    Allan

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  12. #7
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    Hey thats cool did,nt know about availability of two inch eyepieces less than 15mm f/l , will do a search, how good are these orion stratus. if you would , thanks Daniel

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    I will be honest and say since I am primarily an imager, I have little to compare the Stratus eyepieces to except regular plossls, and compared to that, they rock!

    Allan

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    You need a light path that is 2 inches wide........... or more than 1.25 inches wide certainly!

    I do use 2 inch eyepieces in sizes 26mm and "larger" - but 1.25 inch in anything smaller. The light path in an LX90 8 inch is about 1.7 inches so I do gain a little wider field of view by using 2 inch instead of 1.25 inch. The 10 inch LX90 has a full 2 inch internal baffle tube-- most modern mid-priced refractors already come with 2 inch focusers.

    On my LX90 I needed to buy an SCT screw on 2 inch diagonal that replaced the original 1.25 inch diagonal. EVEN the Ethos 13mm --- has a 1.25 inch "insert" inside it's 2 inch tube!

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    Quote Originally Posted by Auburt View Post
    I don't know if i want too, but i really didn't know what specific questions to ask so i just asked a very general question. (I'm a new to this and just trying to figure stuff out.)

    That's fine, I just think it is a good question some people don't ask. If you like large eps, that's good too. Just don't think you are necessarily getting more light from the scope.



    FOV=AFOV/MAG = beam size?

    No, the image size divided by the focal length would be the angle for a single lens. If the image angle is the actual FOV then that angle can let you calculate the size of the lens needed. The image truncates a cone from the last element of the scope.

    For the diagonal, just use similar triangles. Take the distance from center and the distance to the image. The diagonal should be proportional.


    What size Refractor would you need to take advantage of 2" EP"s and also is this true for the diaganol also?
    Using the above and the f/no of the ep tells you the size lens needed. But the f/no of the primary determines whether or not there is a benefit.

 

 
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