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Old Thursday 24th January 2013, 08:21   #26
jan van daalen
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Forgot to mention the inner diameter.
In mm it is 41.2
My Mitutoyo has also an inch scale, which I don't get. An inch is 16 stripes long and in that case it is 1 inch and 10 stripes.
Hope this was of any use.
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Old Thursday 24th January 2013, 09:54   #27
mooreorless
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Hi Jan, Thanks for measuring the extender. These extenders fit the Nikon SE series binoculars pretty tight. Here is a thread by me on comparing the Eagle Optics extender to the Bushnell.

http://www.birdforum.net/showthread.php?t=219014

Lars, I missed how you have that extender ready for action in your picture.
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Old Thursday 24th January 2013, 22:15   #28
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The extender will also fit over the Swarovision eyecups, but the 'friction-fit' is a tad bit loose. Does work well & is much user-friendly than the Swaro doubler on the older ELs.
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Old Monday 28th January 2013, 15:48   #29
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Thank you jan and others. I received my bushnell 2.5 today and was surprised with the quality. As you stated jan, it doesn't fit very far onto the duovid's eyecup but it does stay in place if you are careful. I am thinking about using a small piece of rubber tubing that will stretch to fit on the outside of the duovid eyecup and doubler. I think the tubing would at the very least keep the doubler from dropping off the binos if the friction fit were to fail.

As far as performance goes, the doubler exceeds what I expected. I purchased the doubler with the expectations that it wouldn't replace my swaro spotting scope, but it would work on the long hikes where I don't want to carry the heavy 80mm spotter. I just wish I could have found the doubler for a lesser price. I paid $100 on ebay, that was far less than any other place I could find.

Again, thanks all for the info.
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Old Monday 28th January 2013, 16:27   #30
jan van daalen
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Well if it will make you happy, down here you pay 250,00 euro's, so you got yourself a real bargain.
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Old Friday 19th July 2013, 20:46   #31
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I came across this thread a while back and it got me interested in obtaining a Bushnell Doubler, but by the time I came across it, none were available at a nice price. It has been on my mental watch list ever since.

Today I just happened to spot some for sale at the Bay and Amazon, all from the same seller. Price is $69.95/$69.99 shipped, not as good as the original eBay sell-off, but not bad considering a comment in one of the threads said that the Bushnell Clearance Center had them priced some time ago at $99.xx. I thought I would revise this thread in case there are a few other member who are also interested.

http://www.ebay.com/itm/Bushnell-2-5...-/360597741116

http://www.amazon.com/Bushnell-62-00...shnell+doubler

I ordered one off the Bay listing today. My primary intention is to use it with a now discontinued double hinge Bushnell Elite 12.5X50. That should give me 31.25X! I now need to order a tripod mount to use with a window mount that I have. I saw an old marketing picture where the Doubler was coupled to a double hinge Elite so I am hoping it is a good fit. I am also curious to see how it works with a Nikon EDG-II 7X42. I hope it will provide a situation where I can get all the benefits of the 7X yet still see the detail when needed. It should be fun experimenting with it.

On edit:

Per my PayPal receipt, the above vendor, Asavings, is the Amazon and eBay name for Focus Camera. Here is the listing from their store site:

http://www.focuscamera.com/bushnell-...inoculars.html
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Last edited by BruceH : Friday 19th July 2013 at 23:21. Reason: Added Focus Camera info.
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Old Saturday 27th July 2013, 20:14   #32
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Thanks for the tip, Bruce. I ordered one from Amazon for $69 including shipping. It arrived today. It's a perfect fit on my Zeiss 8x56 FL, 8x42 FL, Nikon 8x32 SE and 8x30/10x35 EII.

It's bigger than I expected, dwarfing the Zeiss Tripler in the photo below. I'll play around with it for a couple of days and right up a little review. I can confirm that it is phase corrected.

Henry
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Old Saturday 27th July 2013, 20:51   #33
james holdsworth
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Originally Posted by henry link View Post
Thanks for the tip, Bruce. I ordered one from Amazon for $69 including shipping. It arrived today. It's a perfect fit on my Zeiss 8x56 FL, 8x42 FL, Nikon 8x32 SE and 8x30/10x35 EII.

It's bigger than I expected, dwarfing the Zeiss Tripler in the photo below. I'll play around with it for a couple of days and right up a little review. I can confirm that it is phase corrected.

Henry
Henry,

I would be interested to hear what you think of the Zeiss tripler - have you reviewed that here somewhere?
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Old Monday 29th July 2013, 19:52   #34
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James,

I reviewed the Tripler here: http://www.birdforum.net/showthread.php?t=156158
and it's compared to the Bushnell 2.5 Doubler below.

Henry

OK, I've had a chance to evaluate the Bushnell Doubler. Like most of these devices it's a roof prism monocular, in this case a multi-coated 2.5x15 with phase correction. Eye relief is a generous 24mm from the glass of the eye lens and about 21mm from the eyecup rim. The eyecup is a modern twist out type. AFOV is around 40.

Unfortunately, unlike the Zeiss Tripler, the Bushnell design renders it pretty much useless as a stand alone monocular. To begin with it's non-focusing and for my eyes the focus is set a little beyond infinity, so I can only achieve a focused image in the field center by wearing 1D reading glasses. Even if it focused the optical quality is pretty poor at full aperture. Center field resolution is barely adequate and there are around 3.5-4 diopters of field curvature, which is quite a lot considering that the field is only 40. The prism is so undersized that a prism edge cuts off part of the exit pupil and there is a bright false pupil right next to the exit pupil which occasionally shows up in the image as veiling glare. Happily all of this, except the field curvature, becomes irrelevant when the Doubler is attached to a binocular and used for its intended purpose. Even the largest exit pupil binocular only uses 7mm of the 15mm aperture, so with a binocular in front acting as a stop down mask the axial aberrations of the Doubler become quite respectable, the prism becomes plenty big enough for the reduced aperture and the bright internal reflections virtually disappear.

I spent a good deal of time comparing the Bushnell Doubler to my Zeiss Tripler, usually with the Zeiss focus adjusted to produce about 2.8x vs the Bushnell's 2.5x. The Tripler is a nifty device, especially with the 8" close focus which allows it to be used as a kind of long range loupe, but in spite of its larcenous street price of $449 Zeiss has never upgraded the AR coatings from the original single-layer "T" coating. So, not surprisingly the multi-coated Bushnell is much brighter with more natural color (brighter I think than the difference in exit pupil alone would explain). Examining a white surface through the objective ends shows a dingy yellowish circle through the Zeiss compared to bright neutral white through the Bushnell. On the other hand the Tripler maintains pretty decent sharpness all the way to the edge of the field (why not?, it's not much over 36). The severe field curvature of the Bushnell (there's hardly any off-axis astigmatism in the mix) limits its critical sharpness to no more than 10 of the 40 field. Bad as that sounds it's actually good enough for the main use I put a thing like this to, which is try to to ID a tiny distant bird too far away to be identified at the magnification of whatever binocular I'm using. A pocketable device that does that is worth the $69 to me.

Last edited by henry link : Monday 29th July 2013 at 20:39.
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Old Monday 29th July 2013, 20:31   #35
james holdsworth
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Thanks Henry, for both reviews.
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Old Thursday 8th August 2013, 03:11   #36
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Originally Posted by henry link View Post
Thanks for the tip, Bruce. I ordered one from Amazon for $69 including shipping. It arrived today............

Henry
Henry ..... Glad you got one and thanks for posting the review covering both the technical characteristics and the practical application.

I have been out of town so I just got mine this evening. It is a good fit the 12.5X50 Bushnell Elite and the 10X43 Elite eyecups. The fit is a firm friction fit. I would not want to hike around with it attached for fear it would fall off, but it did stay attached with light shaking. It also fits the Nikon EDG II, but it does not go as far down on the eyecup because of arrows molded on the rim of the eyecup. It does not take much to remove it by hand so a slight bump could knock it off. To my surprise, it did survive the shake test on the EDG.

Eye placement is somewhat touchy, but quite workable. As expected, the field of view is noticeably smaller than with a straight binocular. The sharpness in the center is not bad with the 12.5, but does deteriorate rather soon. Considering the purpose is to identify something in the center view, I do not see this a problem for my intended use. The center view appeared much larger with the Nikon EDG 7X. I assume the EDG flat field view contributed to that. Actually, the view with the EDG was much better than I expected. My short test was near the end of day so I did loose a some brightness with the 12.5X50 but it was quite bright with the 7X42. Also, the color and contrast where fine, especially with the EDG.

Just for fun, I tried hand holding it with the 12.5X unbraced, and I was able to do it for short bursts. It gives me hope I will be able to view out the truck window without a tripod for a quick ID.

My intended purpose was to have something to fill in for a scope without having to have a scope and it looks like the Doubler will meet that goal. It does not compare in sharpness to a nice scope, but similar to what Henry said, it should work for getting an ID on something when there is just not enough magnification in a straight binocular. This is all in a small package at al low price. I am looking forward to using it out in the field.

Question .... Is there an advantage or disadvantage to place it on one barrel or the other. I ask this because most conventional binoculars have the diopter adjustment on the right barrel. Does this have any impact on the Doubler?
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Old Thursday 8th August 2013, 21:00   #37
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Question .... Is there an advantage or disadvantage to place it on one barrel or the other. I ask this because most conventional binoculars have the diopter adjustment on the right barrel. Does this have any impact on the Doubler?
Obviously there is one distinct advantage to put it on the same side as your dominant eye. In my case, that means the right barrel.
By this, I can use the set as a bi-monocular. First I can look with my right eye through the left barrel with the standard magnification, then I move the set towards left to look through the doubler-equipped barrel.
If I put the doubler on the left side, it's physically impossible to look through the right barrel with my right eye.
If your left eye is the dominant eye, put the doubler on the left barrel.

//L
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Old Thursday 8th August 2013, 23:59   #38
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Could you, conceivably, use two doublers and have a bi-nocular scope?
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Old Friday 9th August 2013, 02:14   #39
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Could you, conceivably, use two doublers and have a bi-nocular scope?
James,

There was a thread here on exactly that subject. It involved using 2 Swarovski Doublers on one of their binoculars and the OP and I had a short discussion about it. Here it is:

http://www.birdforum.net/showthread.php?t=242061

Now, I didn't try this to see if it would work for the reasons I outlined but he seemed convinced!

But it certainly would help if the doublers screw on the binocular like they do on the Swarovski binoculars.

Bob
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Old Friday 23rd August 2013, 06:04   #40
BruceH
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Obviously there is one distinct advantage to put it on the same side as your dominant eye. In my case, that means the right barrel.
By this, I can use the set as a bi-monocular. First I can look with my right eye through the left barrel with the standard magnification, then I move the set towards left to look through the doubler-equipped barrel.
If I put the doubler on the left side, it's physically impossible to look through the right barrel with my right eye.
If your left eye is the dominant eye, put the doubler on the left barrel.

//L
Looksharp65 ..... Thanks for responding to my question. What you say makes sense. I am also right eye dominant.

I noticed in the instructions that Bushnell said if the diopter adjustment is in the center, then put the Doubler on either barrel, but if the diopter adjustment is a ring on the right barrel, then put the doubler on the left barrel. Maybe they are concerned the user may accidentally change the diopter setting. They also said to not extend the binocular eye cup but I seem to have easier eye placement (without glasses) with the binocular eye cup extended. I have not spent much time with it so I need to do some more testing.


****************************************

Here are some photos to show what you get and how it fits a couple of binoculars. The first binocular is a 12.5X50 Bushnell Elite (now discontinued) and the second is a new Zeiss 8X42 HT. The eye cup of the Zeiss appears to be a tad larger so the Doubler does not slide on as far, but it survived the shake test. I also put it on a Zen-Ray 10X43 ED3, but it did not slide on very far and was easy to knock off if bumped.
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Old Friday 23rd August 2013, 15:57   #41
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Lars and Bruce,

I think you’ll find that in nearly every binocular one barrel is better than the other. Usually more coma is introduced into one side in the process of collimation or there may be astigmatism confined to only one side. Whatever the reason, one side will usually have at least a little better resolution and the image will look at least a little cleaner when the magnificaion is boosted. I usually cut to the chase and start by doing a high magnification star test to see which side is the “good” one and then use the booster on that side.

Henry
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