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Attaching a Red Dot Finder OVER a stay-on spotting scope case (1 Viewer)


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Attaching a Red Dot Finder OVER a stay-on spotting scope case

I've always liked the stay-on cases that come with Pentax PF spotting scopes. These provide protection, yet allow quick and easy deployment with zippers and velcro - even providing a pocket in the objective-lens-covering flap to hold the big lens cap when the scope is in use. Additionally, a quick release plate can be left on the protruding scope "foot" so the case-protected scope can be easily secured to a tripod head.

While pointing the "straight-through" models with low power wide fields is simple, aiming the angled models or straight through ones at higher power is more difficult. This is where a red (or green) reflex sight (Red Dot Finder = RDF) can be worthwhile. Unfortunately, mounting such a sight by drilling through the scope body (and releasing the dry gas filling!) is something most scope owners (myself included) would not even consider.

A relatively simple solution to this is to apply a sight-holding 1/4-20 screw OVER the fabric case using a large thumbscrew-tightened hose clamp. While this does require a little do-it-yourself work, no tools other than a hacksaw, file, and drill with bits & countersink are needed. A clamp or vise is useful for holding the parts while working on them. This modification doesn't change the scope or stay-on case at all and can be removed or left on when the scope is transported or stored. Materials needed are just a short piece of 4" sch 40 PVC pipe, a 1/4-20 flat head machine screw, and a 4 1/2" diameter hose clamp with thumbscrew. These are commonly called 4" dryer vent hose clamps and are available from Amazon with plastic or metal thumbscrews. Either will work, but the all-metal thumbscrews won't come off with use. The hose clamps are adjustable from 3 1/2 to 4 1/2 inches in diameter and so can be applied in different positions along the tube and to different scopes. See photos below:

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Photo 1 - Half-inch wide ring being cut from 4" sch 40 PVC with hacksaw

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Photo 2 - 2" long segment of PVC ring being countersunk underneath to fit 1/4-20 flathead screw

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Photo 3 - 1/4" hole drilled in solid portion of 4 1/2" thumbscrew hose clamp

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Photo 4 - PVC segment with shortened flat head screw assembled through hose clamp to mini-ball-head and tightened around scope case. Another unfastened hose clamp with screw and PVC segment is at the left to show how they go together

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Photo 5 - Mini ball head holding RDF attached to hose clamp assembly on Pentax PF-80A spotting scope. BOTH possible mounting positions are shown, but you'll use only one!

Additional notes:

1. There is JUST enough room to apply the 1/2" wide hose clamp in front of the eyepiece but behind the focus knob. I tried that location first and it works nicely, but I now usually mount the finder farther forward, just behind the back of the stored extendable lens shade. This reduces the "look up" distance above the eyepiece and allows better focuser knob access. Try both locations and see which you prefer.
If you use tall eyepieces like the Pentax 8-24 mm zoom, the slightly higher attachment behind the focus knob will position the RDF properly without an added mini-ball-head mount-raising spacer.

For either location, apply the hose clamp OVER the stay-on case. The case can still be opened, closed, and scope attached and detached from your tripod as before. Tighten the hose clamp securely, but don't overdo it.

2. I had initially thought a prism-angled RDF would be better for use with the 45˚ angled spotters, but, after trying that, found it easier to use the unmodified straight through RDF (or a straight through Nydar sight) by just "glancing up" 45˚ from the eyepiece. You just need to "nod your head" upward 1 to 3" (depends on eyepiece height) to see the RDF reticle and aim the scope. A prism-angled RDF IS better for a right-angle-viewing scope.

3. The same 4-inch "dryer vent" hose clamp shown attached to the Pentax PF 80-A will ALSO fit the PF100, PF65-A, and PF65. I have not tried it on a PF80, but should fit that, too.

4. This attachment idea should be applicable to other brands of spotting scopes with stay-on cases, but I have not tried others.

5. I have not tried applying the "hose clamp RDF mount" to scopes without stay-on cases, but it should work for those as well. Applying a 1/2" wide strip of thin, adhesive backed felt to the inside of the hose clamp ring AND/OR applying heat shrink tubing to the part of the hose clamp and PVC section in contact with the bare scope tube should protect the scope finish from damage. Some careful experimentation may be necessary here.

6. For small lower power angled scopes like the Nikon ED50, I still prefer the simple, excellent "cable tie" sighting method described in other Birdforum posts, but this RDF sighting seems better for higher magnification "pointing" and is especially useful when doing outreach with beginners who ask "Just where IS that bird so I can see it with my binoculars?" after looking "down" through the angled scope eyepiece.

7. Low cost RDF's are available from Amazon for a little over $20. These each offer a choice of 4 different reticles and varying brightness levels in red and green. I prefer the circle with central dot in green at full brightness for bright day finding, but go to red at diminished intensity for pointing the scope at dusk or in deep woods. Various "mini ball heads" are available that attach to the hose-clamp-held 1/4-20 screw and allow simple RDF reticle alignment with your scope. One I like and use is the Giotto MH 1004, available online for under $20. A short section of tapped Picatinny rail OR a wooden block with Tee nut is needed to attach the RDF to the mini ball head. See my angled RDF Birdforum post for more information and additional link to Cloudy Nights post with details about making these attachment pieces. Link: Prism modified RDF for ergonomic aiming angled spotting scopes

8. For easiest storage and transport, I usually just unscrew the RDF and leave the hose clamp and mini ball head attached to the scope. When setting up again, once the scope is reattached to the tripod and RDF screwed onto the ball head, it is quick and simple to aim the scope at a prominent point, lock the mount, and move the reattached ball-head-mounted RDF to realign.
-Bill Blunk
Saw a guy with a zip-tie on his ‘scope cover and lined up the "tail" of the zip-tie with the bird (Great White Egret in this case) and it clearly worked and almost free

note - my angled Swarovski 80mm has a little sight built in by the manufacturer which is aimed along the 'scope's axis
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