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Inexpensive 3D views in a binocular telescope

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#1 bcarter1234

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Posted 14 February 2020 - 10:51 PM

I wanted to share an experience from last night to see if it is repeatable for others or just a fluke of my particular observing system from objectives to visual cortex. 

 

While trying to determine the magnification of a pair of eyepieces salvaged from a Tasco Zip binocular. I have 23mm, 20mm and 18mm eyepieces to compare them with. I put one of the Zip EPs in one side and a Vite 23mm in the other of Mr Bill's Bino Box Redux, a 127mm asymmetrical binocular telescope.

 

At first I was just looking at each in turn with my left eye. The salvaged EP had a slightly larger image scale. It dawned on me that both were coming to focus at very nearly the same height so I refocused the right side for my right eye and took a binocular look. The impression of depth was immediate and unmistakable. I was looking at M42 and the stars seemed to really be at various distances. It was like looking at a 3D image in a stereoscope. 

The image is not without flaws as obviously at some point out from center the stars no longer overlap so you see offset duplicates. Still the impression of the object in the center is well worth it.

 

I hope to try soon with some other unmatched EP pairs to see how it works at other separations and if switching sides makes a difference. I'll also see if the same effect is generated in a binoviewer.

 

I hope others will give it a try and share their experience. 

 

Thanks for reading.

 

Take care,

Brent 


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#2 range88

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Posted 14 February 2020 - 11:37 PM

I believe this is the underlying principle of the Denkmeire 3D eyepieces? 



#3 TOMDEY

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Posted 15 February 2020 - 12:20 AM

Interesting! Binocular depth-perception involves differential L/R parallax. Magnification mismatch is similar enough to manifest as something like that... except that the top and bottom of the field will fail to merge. The effective mil-spec allowable mag mismatch is in the neighborhood of half a percent, before it starts to get distracting. Your affective is many times that. Our eyes can tolerate quite a bit, before eyestrain gets intolerable.    Tom

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#4 TOMDEY

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Posted 15 February 2020 - 12:28 AM

I have these --- lot of fun to use!    Tom

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#5 Taosmath

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Posted 15 February 2020 - 01:51 AM

I  had a somewhat analogous experience some years ago, when I was deciding whether to buy BST 19mm Ep's or Agena 20mm SWA for my Denk II.  I purchased a pair of each to evaluate with the idea I would keep whichever set I preferred and sell the other.

 

In the course of the evaluation, to facilitate immediate & direct comparison I put one model in the left EP holder and the other model in the right and was doing some comparison using my left eye when without thinking , I looked through both EP's simultaneously and noticed with a small effort I could align the images and got an apparent 3D view.  I liked the view (of the Double Cluster IIRC) and showed to to my observing buddy, but he complained it gave him a headache.

 

I never bothered to try it again.



#6 bcarter1234

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Posted 15 February 2020 - 09:20 AM

I believe this is the underlying principle of the Denkmeire 3D eyepieces? 

range88,

 

That was my guess as well and further that the purpose of the array on those EPs was to allow most of the stars in the field to overlap and merge properly since images not passing through the array would have the same magnification on both sides. 

 

Tom,

 

That excerpt describes the experience very well though with a bit more clinical detachment than I maintained. I would have written "...and it causes SPACE DISTORTION!!!" ;-)

 

Taosmath,

 

I didn't notice any deleterious effect with regard to eyestrain but that might vary by individual. I didn't concentrate on the stars outside about 50% from center and made no effort to merge them.

 

Let me know if anyone else tries it. Next up the Double Cluster and M45. Anticipating planets and M57 later this year assuming the effect continues when Barlowed.

 

Take care,

Brent




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