Elite 2.5x Doubler (1 Viewer)

I recently started using the Bushnell Elite 2.5x Doubler. My prior experience is with the no-longer offered Eagle Optics 2.5x one. Both are made in Japan.
I do not know anything about how it performs with Bushnell binos.

What i can report:

My primary bino i use it with has a fov of 7.5 degrees. The doubler reduces that to about 3 degrees. It does not change the close focus distance of the bino.

As is true of any good doubler, it will amplify any underlying abberations in the bino.

With a high quality bino (in my case, the Nikon 8x32 SE) it provides a view similar to a spotting scope that is well corrected achromatic (non-ED) spotting scope, at 20x. Of course that bino is about as abberation free as they come, so YMMV.

Do you put the SE on a tripod when you use it with the extender?

Bob

ceasar said:

Do you put the SE on a tripod when you use it with the extender?

Bob

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When i first try it on a bino i do. But generally, no. Hold the bino "vertically", holding its width, up/down. Pretty stable that way. 8x se really stable that way due to its gripability.
I have only used it on the 12x se though, on a tripod.

I couldn't find it on the Bushnell site. Cameraland has it as a special order.

From the photo of it on the CL site (and the price) it appears to be a quality accessory and it looks to be much better constructed than the discontinued Eagle Optics doubler. I had one of those but I found it almost impossible to use on my Eagle 6 x 32 Platinum Ranger so I sent it back. It didn't seat itself solidly on the eyecup and kept jiggling around.

I didn't have an SE at that time to try it on.

Bob

Bought mine from Amazon (They sourced Optics Planet).

Thanks for the heads up. Did you use on the SE with the eyecup rolled down?

spacepilot said:

Thanks for the heads up. Did you use on the SE with the eyecup rolled down?

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Yes. Fit is fine.

Cool, thanks!

On Ebay, the seller Deal-monger has been selling the Bushnell Elite 2.5x doublers for a couple of months with most auctions ending between $28-$45, and they have a buy it now for $89. He usually has a couple of auctions going on at the same time.

http://www.ebay.com/itm/Bushnell-El...390358707668?pt=Binocular&hash=item5ae3312dd4

I have bought 2 of them for around $30 each, and several other members have bought them as well, as they are a great deal.

Tom

The Elite doubler is one of my favorite pieces of gear. I really like it as a means of carrying a small spotting scope when weight is a real factor and even a 50mm scope would be too much.

I have always been very impressed with the high-quality image I get from it. Not in line with a good 80mm scope to be sure, but very useful nontheless.

Thanks Tom just what I needed to be back at the bay spending money. Maybe down the road I'll be able to pick one up for under 40 clams. They do appear to be handy.

Having received one of these from BF member BrightIdea, I much concur with jaymoynihan's findings.

Looking through the doubler w/o having it attached to a binocular, the image is very distorted and it's only reasonably sharp at the very center.
The only binocular that provided a satisfactory image with the doubler was my Zeiss 10x32 FL. Although the sweet spot of the FL series is not actually gloriously wide and the edges cannot really be refocused, this combo gave a very nice image with remarkable edge sharpness.

Somehow, the aberrations of these two instruments seemingly neutralized each other when put together.
Now, a 25x32 wouldn't be anyone's prime Christmas wish. More on that later.

The observation that the doubler multiplies the aberrations of the binocular it's used with seems very valid.
My recently acquired Nikon HG 10x32 was absolutely horrendous with the doubler.
Reason: a very excessive CA. In ordinary use, the CA is not bothersome.
My Vortex 6.5x delivered an image somewhat reminiscent of looking through the doubler - a very distorted image with a minuscule sweet spot.
My Zeiss 10x40 wouldn't hold the doubler because the eyepieces are not wide enough. The image suffered from some straylight, but apart from that, it was pretty sharp and bright. Still, the FL was much better.
The Bushnell Excursion 8x28 wouldn't focus sharp, as far as I could see. Very dull and murky image.

Then I tried the doubler with my Fieldscopes and that was a very encouraging experience. I could push the ED82A to 188x and the ED50A to 100x with no appreciable loss of detail, though I have no chart at hand to perform a more scientific test.
It is clear, though, that these are capable of delivering detail way beyond their ordinary zoom range.
In real use, atmospheric conditions/heat mirage, decreasing brightness and tripod sturdiness will be the limiting factors for seeing the smallest details at great distance.

So, how will I use it? The most apparent use is with the ED82A when I have the 30x Wide DS mounted. The doubler provides a high-quality 75x quick glance without having the need to change to the zoom. And the 50x Wide DS can be boosted to 125x when conditions allow.

If one wants to use the doubler as a serious alternative to a spotting scope, an alpha 8x42 or 7x42 would be the most suitable configuration. If the 8x42 FL interacts with the doubler like the 10x32 does, this would be a killer combo.

//L

Looksharp 65: Is your 10x32 FL the Loutec version? I know that Zeiss changed the eyepiece design when they went to the Loutec version, at least on the 42s. Is the fit of the doubler snug when fitted to the FL eyepiece?

karmantra said:

Looksharp 65: Is your 10x32 FL the Loutec version? I know that Zeiss changed the eyepiece design when they went to the Loutec version, at least on the 42s. Is the fit of the doubler snug when fitted to the FL eyepiece?

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Yes, it is, and it fits very snugly. If I extend the eyecup after fitting the doubler, there's even a suction force when I remove it!

//L

"Then I tried the doubler with my Fieldscopes and that was a very encouraging experience. I could push the ED82A to 188x and the ED50A to 100x with no appreciable loss of detail, though I have no chart at hand to perform a more scientific test.
It is clear, though, that these are capable of delivering detail way beyond their ordinary zoom range."

Lars, I think you have some excellent samples of these scopes.:t:

mooreorless said:

Lars, I think you have some excellent samples of these scopes.:t:

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Ya think so? :smoke:
The ED50A used to belong to Sancho and the ED82A was bought used from a German amateur astronomer saving up for a big APO refractor.
It's wise to choose an honorable seller when you're into used optics like me...

It seems a good quality booster like the Elite is a good tool for determining the central sharpness of sports optics and their associated aberrations.

As a side note, I boosted my FL with the 6.5x Fury and the image was quite good. When I boosted the Fury with the FL...not that good at all! :-O

//L

looksharp65 said:

As a side note, I boosted my FL with the 6.5x Fury and the image was quite good. When I boosted the Fury with the FL...not that good at all! :-O

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The binocular in back has the easy job. Its aberrations are not magnified. In fact, they're typical reduced since its aperture is stopped down to the diameter of the exit pupil of the front binocular. The optical warts of the front binocular is what you see.

Henry

henry link said:

The binocular in back has the easy job. Its aberrations are not magnified. In fact, they're typical reduced since its aperture is stopped down to the diameter of the exit pupil of the front binocular. The optical warts of the front binocular is what you see.

Henry

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Thanks for clarifying that, Henry. I should have mentioned it myself, but assumed that it was obvious. The FL is obviously a much sharper binocular, although this cannot be detected during normal birding use.

Theoretically, would a 7x booster with a top notch 10x show a different result than a 10x booster with a top 7x?
That is, will the sequence of the optical train mean anything if the final magnification is the same?

//L

henry link said:

The binocular in back has the easy job. Its aberrations are not magnified. In fact, they're typical reduced since its aperture is stopped down to the diameter of the exit pupil of the front binocular. The optical warts of the front binocular is what you see.

Henry

Click to expand...

Put your best foot forward, so to speak!

looksharp65 said:

Theoretically, would a 7x booster with a top notch 10x show a different result than a 10x booster with a top 7x?
That is, will the sequence of the optical train mean anything if the final magnification is the same?

//L

Click to expand...

It doesn't matter much. You might think of the front binocular's eyepiece combined with the optics of the back binocular as functioning together like a complex high powered magnifier for examining the tiny image formed at the focal plane of the front binocular's objective lens.

Or maybe it's better to think of the back binocular as an eyesight magnification booster rather than a binocular magnification booster. Point it anywhere, including into another binocular, and thanks to the extra magnification your eye can see details that are invisible without it.

I would suggest that the next step should be to use this technique for a high magnification star test of the front binocular. That should tell you why the Fury isn't as good as the FL.

Henry