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OVL Nirvana 16mm EP - kidney beaning


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10 minutes ago, Stardaze said:

The 22T4 Nagler is held in very high regard I understand John, yet noted that @Louis Dfound there to be some kidney beaning evident in that model too. Was it something you noticed yourself?

Apologies to the OP for slightly veering away from the EP under debate, but it’s interesting that even some high-end EP’s seem prone to this too.

 

It was such a long time ago (13 years ago, maybe) that I owned the 22T4 that I honestly can't recall :dontknow:

I remember it being an easy to use eyepiece with good eye relief and a nice big eye lens to gaze into. One of the first premium eyepieces that I owned.

 

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46 minutes ago, Stardaze said:

The 22T4 Nagler is held in very high regard I understand John, yet noted that @Louis Dfound there to be some kidney beaning evident in that model too. Was it something you noticed yourself?

As for me, I find the kidney beaning very moderate to unnoticeable in use.  Despite having the same size eye lens and AFOV as the other two NT4s, it does have longer eye relief making it easier to use with eyeglasses.  Back to back comparisons over multiple sessions led me to oust the Astro Tech AF70 22mm from my A-team case and replace it with the 22mm NT4.  It has a bit less eye relief (about 2mm less), but it is significantly sharper at the edges.  The centers are roughly equivalent.  The wider AFOV of the NT4 sealed the deal to live with the tighter eye relief.

Edited by Louis D
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I have an 8" F6 dob too and I am enjoying my gradual transition to 82º EPs.

Maybe it is the 'gradual' transition that has made the difference?

With several of the EPs I have other people have suggested that there are difficulties.

I'm very fortunate not to have experienced them.

I have the 7mm, but not the 16mm, because I already have a 14mm and that's lovely.

The wider FOV does take a little getting used to and yes, you do have to move your head to get the full FOV.

I hope you find a solution, or settle on a FOV that you are more comfortable with. :)

 

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SAEP is more of a problem when the eyepiece has a large exit pupil and less of a problem with a smaller exit pupil, though I don't think there is a hard cutoff on that scale.

I wonder, but have never read anything about it, whether spherical correction (myopia or hyperopia) in the eye can influence one's sensitivity to it.

 

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1 hour ago, Don Pensack said:

SAEP is more of a problem when the eyepiece has a large exit pupil and less of a problem with a smaller exit pupil, though I don't think there is a hard cutoff on that scale.

I wonder, but have never read anything about it, whether spherical correction (myopia or hyperopia) in the eye can influence one's sensitivity to it.

 

It tends to be an issue until fully dark adapted so your iris can take in the entire exit pupil.

I know presbyopia has little to nothing to do with it because eyepieces with SAEP looked the same to me before I got it and after.

What I'm trying to figure out is why SAEP is more noticeable in slower f-ratio scopes.  Perhaps something to do with the combined exit pupil size between the scope and the eye?

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Hmm.  Exit pupils will be smaller in longer f/ratio scopes.  One would think that the smaller exit pupils would make SAEP less noticeable, as astigmatism is.

I'll have to think about that.

But, presbyopia doesn't influence spherical correction much, if at all, though if it is strong enough to prevent accommodation at distance as well as close up,

it will make a difference in where the scope focuses.  I haven't noticed much difference, as my vision has drifted toward fixed focus, to my sensitivity to SAEP.

The eyepieces that were bothersome are still bothersome.

Have you?

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