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Magnifying Finder Scope for 25x100 Binoculars

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#1 at_home


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Posted 02 April 2012 - 02:09 PM

The 25x magnification of 25x100 binoculars is wonderful for seeing objects with both eyes, but the resulting 2.5 degree field of view can make it difficult to locate objects (especially for beginners). A red dot finder helps for bright objects, but a magnifying finder is better for dimmer objects.

There are two obstacles to overcome, though.

1. Most magnifying finders (whether straight or right-angle) give an image with a different orientation to binoculars. It would be nice to have an image with the same orientation.

2. It's difficult to find an adapter to mount a magnifying finder onto a pair of binoculars.

Since I've learnt a lot from the Cloudy Nights Forums, I wanted to give something back by sharing a set up which overcomes these obstacles - an Orion 10x42 monocular attached to giant binoculars using a Pedco UltraClamp Assembly (see attached image).

The Orion 10x42 monocular has a 5.9 degree field of view, so star hopping and locating objects is much easier than with the 25x100 binoculars. It has internal prisms so the view has the same orientation as the binoculars - it's nice to have different magnifications of the same view by moving between the monocular and binocular. Furthermore, the monocular is straight through so it's easy to move between the two.


The Pedco UltraClamp Assembly can clamp to the center rail of 25x100 binoculars and hold devices with a 1/4"-20 tripod socket. Fortunately, the Orion 10x42 monocular has such a socket. The UltraClamp also includes a ball and socket mechanism for aligning the monocular to the binoculars. While it should be possible to use the UltraClamp to mount a small pair of binoculars (e.g. 8x42) to the 25x100 to achieve a wider field of view (e.g. using an additional tripod adapter), this arrangement is heavier so I haven't tried this yet. It's also possible to mount the monocular onto 20x80 binoculars with a center rail but the wider 3.2 degree FOV makes this less important.


I hope I'm not duplicating a previous message and I hope this arrangement can benefit other fans of giant binoculars.

Clear skies,


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#2 Rich V.

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Posted 02 April 2012 - 04:55 PM

That looks like a creative solution, Andrew. The monocular's correct orientation will be a plus when used as a finder.

I've been fortunate that my relatively dark skies provide plenty of reference stars and red dot or multi-reticle finders are all I need to find my way with my big binoculars. With LP skies an optical finder can really come in handy.

Enjoy, and welcome to Binoculars!


#3 GlennLeDrew


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Posted 02 April 2012 - 06:34 PM

Nice idea! Of course, one must be careful of breathing on the bino's eyepieces, at least in chilly conditions, so as not fog them up. I suppose a way to minimize this is to have the finder mounted more to the side rather than directly above...

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