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extenders (1 Viewer)

mooreorless

Well-known member
Bushnell and Eagle Optics 2 1/2 extender

I read Jay's thread about the Bushnell 2 1/2 extender and I had given my Eagle Optics 2 1/2 extender to someone and sort of missed it.
http://www.birdforum.net/showthread.php?t=214376

I saw posts on here about buying these Bushnell extenders at a cheaper price off Ebay, thanks to Lilcrazy's posts and other people. I ended up winning one of the Bushnell extenders. I thought it might be interesting to compare this Bushnell extender to my old EA extender. I asked if I could barrow my old one off the person that has it now and they graciously agreed to send it back to me. I am sure most people know what binocular I have these mounted on.:)
 

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mooreorless

Well-known member
I used my USAF chart checking out the elements I could read. This was done over quite a few days. I didn't worry about distance trying to see what the maximum resolution was or anything just comparing the two extenders. I found that the Bushnell extender had better contrast than the Eagle Optics extender. The Bushnell extender could usually go down one element lower on the chart. I did try to measure today and it was very cloudy here today, but was able to measure, of course the readings would be lower in lower light levels and really you need more than 20x to measure resolution on the Nikon 8x32SE. 3.5 sec for the Bushnell and 3.9 sec for the Eagle Optics. I have found with the Eagle Optics extender that if you didn't line it up with the exact center I could almost read with the Bushnell. The Bushnell is supposed to be phase-coated and the EA is not. Without either extender the difference was 5-6 elements larger. I see a small Verizon mini substation about 200 yds. from my back porch, I could read the word Verizon with both of these extenders, I could not come close to reading this without the extenders.
Looking outside now, of course the Sun is out.

I tried using the two extenders as an extended binocular and I made it work, this was w/o glasses and really not much fun.
 

mooreorless

Well-known member
Sunday it was sunny here and I tried doing a 20x star test for giggles. Here are some photos. Well my poor excuse for photos.
Bushnell is the two on the left and EO the two on the right, I messed up the one EO photo
 

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mooreorless

Well-known member
I think these extenders are worthwhile to buy as long as they fit your eyepiece ok and you have a very good binocular in the first place. The Bushnell extender fit the 8SE eyecups better than the EO one.
 

jaymoynihan

Corvus brachyrhynchos watcher
Interesting. My informal impression also was that the Bushnell was somewhat better than the EO. Your posts raised my curiosity about using say 2 extenders of the same brand on the 8xSE....hummmm
 

mooreorless

Well-known member
Hi Jay, It might be better with two of the same extenders, but I don't know if I would want to use them very long.

Forgot to say I had compared my Nikon 50ED with the small zoom set to 20x or at least with the marks lined up and the 50ED had better contrast and could see 1 to almost 2 element below. With it set at 30 I would have to move the target out further. It wasn't as bad a comparison as I thought it would be.
 

mooreorless

Well-known member
Hi Ron, I just tried it and yes very similar edge performance. I never tried comparing the ED50 field of view with either of the extenders mounted on the 8SE. The small Nikon zoom has a sort of mark for 20x.
 
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Surveyor

The more I understand, the more I understand why I
Thanks Steve, the edges are not a problem as an extender, just more than I expected for such low power.

With the 8x bino I would expect about 1.9 degrre FOV. Probably a little more for the ED50 wider eyepiece.
 

mooreorless

Well-known member
I took some pictures of these two extenders, using polarized sunglasses and monitor . Not as good as Henry's. The Eagle Optics extender on the left and Bushnell on the right. This was looking through the objective side of the both extenders.
I waited until after 5:05 here [Dec. 26,2011]to check for lower light use of these and found I could still see 4 or 5 elements lower. I didn't try until dark, I had other things to do. I was happy with that outcome.
 

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henry link

Well-known member
Steve,

Nice work. The Bushnell certainly looks like the class act among the universal extenders. I can't really see anything to be gained by spending far more for the Swaro extender. I suppose the Zeiss Tripler is a little more useful since it can be focused down to about 6". I use mine as a sort of long range loupe as well as a normal monocular, but the $450 street price is pretty ridiculous for a little gadget like that.

Henry
 
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mooreorless

Well-known member
Thanks Henry! I agree about the Bushnell extender being a class act. I paid $79+ shipping for the EO extender when they were closing them out, about 1/2 of that for the Bushnell. The Bushnell fit the 8SE better and seemed to be more centered. Both held upside down.
 

John Dracon

John Dracon
Folks - Have had and used the above mentioned extenders in various and sundry ways. My subjective opinions. The 2x of the Swarovski is too costly, but it is more useful if one owns the appropriate model since the optical path is always in alignment and the binocular only suffers a 50% reduction in the exit pupil. But it requires more fiddling around removing the eye piece cover and screwing in the adaptor. I adhere to the belief that more individual pieces results in more dropping and fumbling around.

The Zeiss 3x is simply too much power for most binoculars, not to mention the premium cost of purchasing one. When it is attached to a 10 power bino, things get a little bit ridiculous for eye placement with such a reduced exit pupil.

The Eagle Optics 2.5x is OK, but barely.

The Bushnell Elite 2.5x is quite good, but it must be attached to a quality bino as mentioned above. Its fit, however, is not universal. But for momentary use it does fit the Nikon SEs and EIIs rubber eye pieces.

The use of two extenders, IMO is just for playing around. No harm done but hardly practical.

Used with a good 7x50 bino, the extender would not compromise the brightness and qualiity of the image so much, but the old 7x50 are going the way of the dodo bird.

Forty seven years ago, Bushnell imported an extender called the Booster 2.5x This contraption fit over the objective beauty caps with friction fit with a nylon screw to snug things up. It looked funny, but actually is very easy to use. For one thing the binocular can be held against the face, making things steady instead of balancing the binocular on one side as with current extenders. Getting on target is easier too since the full view is available from one barrel. Selecting the dominant eye for the barrel being magnified helps too. The ergonomics of the current extenders are not good. Useful IMO for only a quick look in the field. The Bushnell Booster was simply ahead of its time.

John
 

henry link

Well-known member
John,

In defense of the Zeiss Tripler I would point out that, when used as an extender, its magnification factor, unlike the Swaro and others, can be changed from about 2.8x to 3.8x by simply rotating its focuser and then refocusing the binocular. If that much magnification seems to be "too much power" that's a good indication that the binocular in front of it has high aberrations or defects when used at full aperture. That's often the case, but a few binoculars have low enough full aperture aberrations to hold up pretty well at exit pupils as small as 1.5-1mm. The 8x32 SE, for instance, can still produce a pretty decent image even at 30x. The price is certainly too much.

Henry
 
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ronh

Well-known member
Although I don't have or want an extender, I enjoyed this discussion. Thanks for the work and report Steve. Your photos are so interesting that they got me wondering about the whole business of phase coating.

The polarized images show the presence of very good phase coating on the Bushnell and absence on the EO. But the star test images look very out of focus--is that really what I'm seeing? They show something screwy with the EO doubler, but not the fabled doubling of the central diffraction spot.

I think I've seen only one image that showed that. Henry or RonW or anybody, have you ever seen that effect with a non phase coated roof prism? What is the best resolution that can be achieved without phase coating?

When I have looked (only briefly) through non phase coated roofs, my immediate reaction was, golly, is this really so bad? Are we perhaps being sold a bill of goods, another invisible improvement? Say it ain't so, pa.

It is tempting to attribute the performance of the Bushnell to its phase coatings, but how can we be sure?
Ron
 
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mooreorless

Well-known member
Hi Ron, I wasn't going to post my lousy start test images, I could see more in focus with my eyes, I was sort of glad that they looked sort of round more than anything. The EO side showed the line, I guess that was the non phase-coated roof prism.? I did notice using the EO extender that if I rotated it to a certain spot I could see the chart lines better. This would be off center, in other words slightly to the right from center or left.
Ron I had an old non-phase coated Swarovski 7x30 SLC that even Brock liked, but comparing it to my 8x30SLCneu the contrast was better in the neu. I have a Nikon 7x35 Action porro and this 7x30SLC was better than that 7x35 Action.
Ron I have one of the Nikon 8x30 camo Trailblazer non-phase coated I will try to take a picture the same as the extenders.
http://www.adorama.com/NK830RC.html
 
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ronh

Well-known member
Steve,
Thanks for your experiences with the nonPC SLC. I recall some reports of Zeiss Classics that were identical except for the PC, which was judged a good improvement.

I think it will take more boosting than the 2.5x extender to get a good look at an 8x30's star test diffraction pattern. 8x as a booster would get the exit pupil down to 0.47mm which would be about right. Even if you don't get a picture, I would like to hear what you see.
Ron
 

mooreorless

Well-known member
Hi Ron, That was the Nikon 8x32SE I was using with the boosters. I agree need more boosting for the star test, I was just showing the different between the extenders. I did manage to take some not so good images of the Nikon 8x30 non p-coated and Swaro 8x30 SLC neu showing the difference. The black round area to the left on both images is part of the picture from post #11 on this thread. I think this shows quite a difference with the Swaro on the right.
 

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