Making Finder Scope out of old 7 x 50 Binos

I have an old pair of 7 x 50 binos from the late 1960's. The focuser casting broke and the eyepieces fall out! These were my first astro binoculars and the optics are coated and pretty good. I don't want to just toss them out, and I could use a better finder scope, maybe using the prisms to make a 90 degree finder scope.

Are there any plans how to make such a beast? Any help on disassembling the old binos?

You help is appreciated.

Rick Wiseman

Look at the finders Gary Russell Makes - they are bino "fronts".

I've made finders out of 7x35 and 10x50 binoculars. I think they work far better than any commercial finders. The straight-through, erect and correct view makes it much easier to locate objects compared with either inverted-view or 1x finders.

The trickiest part to disassembling the binoculars was removing the central focusing mechanism (it sounds like you may already have that problem solved). Starting with Orion "Outsider" binoculars, I used a hammer and a large bolt to remove a tube that was tightly press-fitted inside the rings holding the two sides of the binocular together. Once this was done, you end up with a pair of rings attached to the body of the binocular, and another ring attached to the eyepiece. You can use a bolt and some nuts and washers to hold the eyepiece in place.

One other problem that needs to be solved is to provide crosshairs or something similar to mark the center of the field of view. Instead of crosshairs, I used a tiny machine screw (#0 I think), sharpened at the tip, driven into the focal plane from the side. This works better than crosshairs because the screw is visible in dark skies without illumination.

For a dewcap, I attached a PVC pipe coupling. To attach the finder to the scope, the dewcap is attached with a bolt, and the back end is attached with a pair of turnbuckles. This provides a very solid mount that is easy to adjust even with gloves on.

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