Red Dot Sights (Reflex Sights) on Spotting Scopes (1 Viewer)

Vollmeise · Jan 12, 2018

To shape the snap on bracket more sturdy, you could place a kind of elastic hinge, like in my draft below. This would lower the risk of material fracture when bending. The thickness of the hinge could be lower than the rest of the collar (unlike my sketch shows).

Hauksen · Jan 12, 2018

Moin!

Vollmeise said:
To shape the snap on bracket more sturdy, you could place a kind of elastic hinge, like in my draft below. This would lower the risk of material fracture when bending. The thickness of the hinge could be lower than the rest of the collar (unlike my sketch shows).

Excellent sketch. I'm beginning to get some doubts: Tightening the screws will stretch the material and give a realiable mount to the scope. However, it will also move the anchor posts relative to each other.

I'm also thinking that maybe round psots are not optimal. Prism mountings like the NATO rail or the various astro rails have the advantage you can be sure that the two parts align each other parallel to a defined surface, while with a circular post, you only get a single contakt line at a not so clearly defined position.

Something like this perhaps:

That leads me to the thought that the snap-on bracket needs to be under constant tension when mounted. In my design program, that probably means that I have to make it a bit smaller than geometrically matching. Otherwise, it will probably "rattle" around in the tolerances.

Tschüs!

Henning

Torchepot · Jan 12, 2018

Just a thought - this design looks like it will be specific to the Kowa scope. If the part that is fixed to the scope (semi)permanently was more like Henning's original bracket but was instead strapped around the barrel of the eyepiece (with a snap on connector for the rest of the sight mount) then it could probably be adapted to fit almost any angled scope.

Hauksen · Jan 12, 2018

Hi Torchepot,

Torchepot said:
Just a thought - this design looks like it will be specific to the Kowa scope. If the part that is fixed to the scope (semi)permanently was more like Henning's original bracket but was instead strapped around the barrel of the eyepiece (with a snap on connector for the rest of the sight mount) then it could probably be adapted to fit almost any angled scope.

With the zoom eyepiece, there are just a few millimeters available that don't turn when you zoom, so I' afraid it's not very practical.

As there seem to be no standard dimensions between different scope types, I'm not very optimistic it will be possible to design a standard mounting.

My original bracket can be customized (before 3D printing) to fit any scope with a cylindrical tube below the pull-out dew cap, but of course it's incompatible with about any stay-on case. Other than that, I'm pretty happy with it. (It might be worth a thought to make the "tower" removable with an astro-style dovetail rail at the base.)

Regards,

Henning

Torchepot · Jan 12, 2018

Hi Henning

I'm not too familiar with the Kowa zoom - when you say a few millimetres wouldn't that be enough? If the fixing was a bit like a cable tie it could fit any size diameter eyepiece. A tiny block of plastic with a snap on attachment for the rest of the mount and a reusable cable tie might be a very cheap and simple option.

Cheers

Phil

Hauksen · Jan 12, 2018

Hi Phil,

Torchepot said:
I'm not too familiar with the Kowa zoom - when you say a few millimetres wouldn't that be enough?

Maybe for avoiding rotation around the barrel axis, but I fear you'd get elastic deformation leading to elevation misalignment.

The attachment ring version has the advantage of fitting against a surface on the body.

Of course, you could try and combine clamping around the threads and around the eyepiece. However, I'm not sure that would gain much, and you'd lose the option to change the eyepiece with the adapter mounted.

For the Kowa, another possibility would seem to be a mounting running around the scope exactly where the black band of the tripod mount is. This would probably fit into the stay-on case, but most likely prevent rotating the scope around the longitudinal axis.

Regards,

Henning

Torchepot · Jan 12, 2018

Had a closer look at the Kowa and the collar for the TSN-PA7 looks ideal

http://www.kowaproducts.com/digiscoping/TSN-PA7_DSLR_Digiscoping_Adapter/

Nice and secure with plenty of room to attach a mount. I don't know if the collar is available separately though?

Hauksen · Jan 12, 2018

Hi Phil,

Torchepot said:
Had a closer look at the Kowa and the collar for the TSN-PA7 looks ideal

Good find!

(In fact, Kowa could probably add a little NATO rail to the TSN-PA7 main part, and our problem would be solved

Regards,

Henning

Torchepot · Jan 12, 2018

You should suggest it to them (remember to ask for royalties)

Hauksen · Jan 12, 2018

Hi Phil,

Torchepot said:
You should suggest it to them (remember to ask for royalties)

I've actually been in contact with Kowa Germany. They said they have seen quite a number of home-built sight mountings, but usually these were based on metal bars mounted between tripod and scope, using extra-long tripod screws, and didn't work so well. They liked my "big clamp" mounting, and even gave me a free stay-on case to cut apart and re-work to fit the mounting.

I haven't done that yet because I keep coming up with new ideas for different mountings. (And because I heard sewing is a difficult skill to learn! ;-)

Here's my favourite from last year ... it would have required a hole in the left-hand side of the rear of the stay-on case:

It's not finished, so the screw connections etc. are not included. I also planned to reduce the long arm to a very short one with the rail rotated by 90 degrees to mount the sights sideways to save weight and space. However, Vollmeise's accessory mount idea at the moment seems to be more promising!

Regards,

Henning

Torchepot · Jan 12, 2018

That's very encouraging that they gave you a case - maybe you could contact them again and see if they'd give you a couple of collars from the TSN-PA7 (one for you and one for Vollmeise

)

Between you I'm sure you could make something that they might be interested in producing as an accessory.

Hauksen · Jan 12, 2018

Moin!

Vollmeise said:
To shape the snap on bracket more sturdy, you could place a kind of elastic hinge, like in my draft below. This would lower the risk of material fracture when bending. The thickness of the hinge could be lower than the rest of the collar (unlike my sketch shows).

Looks like a turtle! ;-)

It's good advice, though. On my digiscoping adapters, I really made the parts I intended to bend too stiff so that it's hard to get the phone in and out :-/ Pays off to shape the part to exploit the elastic properties, I was slow to learn that.

Trying to incorporate the "prism mount" idea, I found that the central part actually doesn't need to bend, only the "legs". Here's what it looks like ... note that the flats of the "U" are deliberately wider than those on the ring:

Does this look workable to you?

Tschüs!

Henning

Vollmeise · Jan 12, 2018

Moin!
I think the last prism mounted version will be much less sturdy regarding rotation than the 4-pin-snap-on version. These kink points of 45° won't deliver much resistance and furthermore just very few force against snapping off by accident.

I'm thinking about quite another version now, kind of a permanent collar with a "hot shoe" mount, like for photographic flash devices. The "Flash" aka red-dot sight (or other accessories) will be inserted from above and held down by a simple self locking latch mechanism.

Hauksen · Jan 13, 2018

Moin!

Vollmeise said:
I think the last prism mounted version will be much less sturdy regarding rotation than the 4-pin-snap-on version. These kink points of 45° won't deliver much resistance and furthermore just very few force against snapping off by accident.

Hm, I'm envisioning it as being self-centering against rotation, as rotating it off-centre will lose contact on all flat faces simultaneously. That's just the picture in my head though, maybe round posts are really better.

With "snapping off", do you mean "detaching" or do you mean "breaking off"? I think the "spring" of the printed parts is quite good. This adapter has a very long and thin "tail" which needs to be bent a little to accept the phone, and it's still a bit too stiff for my liking:

Vollmeise said:
I'm thinking about quite another version now, kind of a permanent collar with a "hot shoe" mount, like for photographic flash devices. The "Flash" aka red-dot sight (or other accessories) will be inserted from above and held down by a simple self locking latch mechanism.

Sounds like that might eliminate the rotation problem entirely.

Are you familiar with the astro rail stuff? Some drawings here (but they seem to come in many varieties):

https://www.highpointscientific.com/stellarvue-50-60-mm-finder-scope-rings-for-sct-telescopes-r50st

Tschüs!

Henning

Vollmeise · Jan 13, 2018

Moin!

Hauksen said:
Hm, I'm envisioning it as being self-centering against rotation, as rotating it off-centre will lose contact on all flat faces simultaneously.(...)

This is true, as long as there are just weakly acting forces. The contact is a frictional connection only, with a very low coefficient (plastic surfaces) in addition.

Hauksen said:
With "snapping off", do you mean "detaching" or do you mean "breaking off"? I think the "spring" of the printed parts is quite good.

I meant detaching. The round openings all of our various designs enclose the cylindrical pins in a way which enables a positive connection. Positive connections are to prefer relating to sturdyness (In German: vgl. Kraftschluss / Formschluss).

Relating to your very last design posted (post 72): if I try to pull the yellow clamp to the left (to detach), the 45° angle of the four prism surfaces will lead more than 70% of the force (sin45° x F x frictional coefficient) sidewards causing the yellow clamp's shanks to open. The opening of the shanks depends on the material's elastic modulus (E-Modul) and shape then.

Using positive connections and no details leading forces in unwanted directions will provide less surprise, I guess

Hauksen said:
Are you familiar with the astro rail stuff? Some drawings here (but they seem to come in many varieties):

https://www.highpointscientific.com/stellarvue-50-60-mm-finder-scope-rings-for-sct-telescopes-r50st

I'm not familiar with that, they look interresting! And by the way: did I thank You for the two links to meltwerk and shapeways? They gave me great inspirations too, thanks for that!

Tschüss!

Hauksen · Jan 13, 2018

Moin!

Vollmeise said:
The round openings all of our various designs enclose the cylindrical pins in a way which enables a positive connection. Positive connections are to prefer relating to sturdyness (In German: vgl. Kraftschluss / Formschluss).

If I understand your drawing correctly, your idea is to make the clamp envelope each of the posts individually at more than one side?

Vollmeise said:
Relating to your very last design posted: if I try to pull the yellow clamp to the left (to detach), the 45° angle of the four prism surfaces will lead more than 70% of the force (sin45° x F x frictional coefficient) sidewards causing the yellow clamp's shanks to open.

That's the way to detach it, so I'm fine with that

It would probably come off if someone would try to use the sight mounting as a carrying handle, but considering the way the fixed clamp is attached, the forces acting on the mounting should be minimized by the user to begin with.

Vollmeise said:
I'm not familiar with that, they look interresting! And by the way: did I thank You for the two links to meltwerk and shapeways? They gave me great inspirations too, thanks for that!

Glad you found them useful! Maybe I should also point out thingiverse.com - it's not a printing service, but you can find and download many designs made by others there. Can be inspiring, too!

Tschüs!

Henning

Hauksen · Jan 14, 2018

Hi again,

Here's the completed snap-on adapter:

I kept the prismatic mounting since I believe it might work.

I'll have to cross-check everything before contemplating printing, though - first time ever I've used OpenSCAD, I'm not sure I got all of the dimensions right.

Regards,

Henning

Hauksen · Jan 15, 2018

Hi again,

Here a version with a dovetail connection:

It would be a bit cheaper than the snap-around version due to using less machine volume. This might come handy for trying out different adapters, like the "long" mount at 12 o'clock and the short one at 3 o'clock (for which the clamp ring would have to be rotated by 90 degrees).

I still need to make up my mind on how to clamp down on the dovetail. The Astroadapters use a big screw through the side of the dovetail, which is not exactly "snap on", but close enough. (It only pushes against the side of the dovetail foot and doesn't thread into it.)

Regards,

Henning

Hauksen · Jan 19, 2018

Hi again,

Vollmeise said:
The sight itself can be mounted and detached, all I need is a 3mm hex wrench.
Maybe I'll replace the hex socket screws by knobs one day to be more independent in the fields..

It just occurred to me that it would be possible to 3D print a new mounting ring for your adapter arm, in case you'd like to switch over from the "screw-down" variant to the "clamp-on" variant.

Here's a picture, with preliminary measurements (10 mm x 10 mm slot, M3 screw), but easy to adapt to the actual measurements of your adapter arm:

Regards,

Henning

Hauksen · Jan 24, 2018

Moin!

Hauksen said:
View attachment 650917

Here the freshly printed part (from Shapeways) ... slightly modified versus the above drawing:

Mounted, eyepiece not yet installed:

Mounted, eyepiece installed:

Mounted, sight installed:

Mounted, overload test! :-D

The overload test shows that a a 450 g heavy target scope is too heavy for the adapter in its current simple form. I'd have to beef it up to carry such a heavy sight.

However, the normal red dot sight weighs just 132 g, and the adapter works just fine for that. (This includes the 24 g NATO-to-dovetail adapter you'd not normally need for a NATO-compatible sight.)

Regards,

Henning

Red Dot Sights (Reflex Sights) on Spotting Scopes (1 Viewer)

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