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Thread: Why do different sites have different specs for the same eyepiece?

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    Default Why do different sites have different specs for the same eyepiece?



    I'm looking into getting a 32mm Meade 4000 Super plossl for my new Orion XT6 Dobsonian. And I want to get an eyepiece with good eyerelief. but the problem is that different websites show different specs for the same fricking eyepiece and Not by 1 or 2 mm off either. Meade's own website shows that it has 26mm of eye relief(way too long) and 52 field of view and Astronomics.com shows the same eyepiece at 13mm eye relief(way too short) and 49 field of view. Telescopes.com shows it at 20mm eye relief. And other websites show these 3 same figures which vary based on the site.

    My 15mm Plossl and my 26mm plossl also have varying specs based on the site.

    Does anyone know what's up with this?

  2. #2
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    Default Re: Why do different sites have different specs for the same eyepiece?

    I would suspect that the 26mm is closer to being correct. It being a 4 element, 2 group plossl design, the typical eye relief runs around that area. (low to mid 20's) Manufacturers seem to have a grey area of calculating exact eye relief that always meets with some disagreement. (my Televue is stated at 22mm) The AFOV from 49-52 is really negligible, as a couple of degree will never really be noticed in the view. 50° is the accepted norm for the plossl design however.
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    Default Re: Why do different sites have different specs for the same eyepiece?

    Some lazy SOB updating their website database probably did a cut & paste into several different listings, and then only changed the focal length, instead of all the specs. Happens all the time in online listings, not just for astro equipment. Some vendors solve the problem by not listing any specs at all.

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    Default Re: Why do different sites have different specs for the same eyepiece?

    If the Meade "Superplossl" is a Plossl (4 lenses 2 groups) then the eye relief should be half the focal length. IF.

    Another if is that sometimes Superplossl means a pseudo Masuyama design (2-1-2, instead of 2-2) which would give a longer eye relief.
    Last edited by not_Fritz_Argelander; 12-28-2018 at 10:34 PM.
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