Kowa Reticle Eyepiece... Let's get to work!

[308pirate]

Has anyone ever tried to get a company like the former Premier Reticles to do a mod to an existing eyepiece? If Kowa won't maybe someone else would if we could get enough people to commit to an order.

I'd be in like Flynn

Let's start a list of who has the technical capability to do so.

Maybe people like @gr8fuldoug or @koshkin would know some?

 

[ken226]

I'd be in like Flynn

Let's start a list of who has the technical capability to do so.

Maybe people like @gr8fuldoug or @koshkin would know some?

Baader Planetarium makes high quality eyepieces, and makes an adapter to allow their eyepieces to be used on tsn770 and 880 scopes.

1¼" / M41 Eyepiece-Adapter for Kowa TSN 770 / 880 Spotting Scopes

1¼" / M41 eyepiece clamp for Kowa spotting scopesenables connection of all Baader 1¼" eyepieces (Morpheus 76°, Hyperion Zoom, Hyperion 68°, Classic-Ortho) onto KOWA-Spotting Scopes and KOWA-Barlow lenses. Also suitable for any other astronomical 1¼" eyepi

www.baader-planetarium.com

I don't doubt it would be within their abilities as they already make an astronomical eyepiece with a reticle. And, it's even illuminated!

Baader 1.25" Micro Guide Eyepiece - 12.5mm # MGUIDE 2404300

Baader 1.25" Micro Guide Eyepiece - 12.5mm # MGUIDE 2404300

agenaastro.com

Their Hyperion line of eyepieces have a good reputation amongst birdwatchers and astronomical telescope users.

 

[ken226]

@99106
@308pirate

I was thinking about the possibility of making an adapter to allow the fitment of either a Burris or Optolyth reticle eyepiece to a Kowa.

Since I dont own a Kowa, I might need some info from someone who owns one to see if this is possible.

If my research is correct, the Optolyth scope body has a 445mm focal length, the Burris signature and Vortex RZR-A1 scope bodies both have a 457mm focal length (the Burris eyepiece fits both). The Kowa TSN880 body has a 500mm (this number isn't from a reliable source) focal length.

If that's all correct, then the eyepiece focal length is S/e=m. Where S is the body focal length, e is the eyepiece focal length and m is the magnification.

So, the for the Burris/vortex 457/e=30. Which puts the Burris reticle eyepiece at a focal length of 15.2333mm.

So, if the tsn880 has a focal length of 500mm, then the adapter would need to move the Burris eyepiece far enough rearward that it would achieve an eyepiece focal length of 16.6666mm. that should achieve a 30x image, resulting in the reticle subtensions being correct.

So, to fit the Burris eyepiece into the Kowa body, the hole in the Kowa would need to be big enough in diameter to allow the Burris eyepiece to fit inside, with enough room to spare, for the adapter.

I've never seen the hole in a tsn880 scope body. Is it a bayonet mount or threads? If threads, what is the diameter and pitch?

I have an Optolyth reticle eyepiece. It has m37x.75 threads. (37mm major diameter x .75mm thread pitch).

I don't have a Burris reticle eyepiece, but I believe the bayonet barrel diameter is about 27mm.

Or, am I barking up the wrong tree with this idea?

 

[308pirate]

@99106
@308pirate

I was thinking about the possibility of making an adapter to allow the fitment of either a Burris or Optolyth reticle eyepiece to a Kowa.

Since I dont own a Kowa, I might need some info from someone who owns one to see if this is possible.

If my research is correct, the Optolyth scope body has a 445mm focal length, the Burris signature and Vortex RZR-A1 scope bodies both have a 457mm focal length (the Burris eyepiece fits both). The Kowa TSN880 body has a 500mm (this number isn't from a reliable source) focal length.

If that's all correct, then the eyepiece focal length is S/e=m. Where S is the body focal length, e is the eyepiece focal length and m is the magnification.

So, the for the Burris/vortex 457/e=30. Which puts the Burris reticle eyepiece at a focal length of 15.2333mm.

So, if the tsn880 has a focal length of 500mm, then the adapter would need to move the Burris eyepiece far enough rearward that it would achieve an eyepiece focal length of 16.6666mm. that should achieve a 30x image, resulting in the reticle subtensions being correct.

So, to fit the Burris eyepiece into the Kowa body, the hole in the Kowa would need to be big enough in diameter to allow the Burris eyepiece to fit inside, with enough room to spare, for the adapter.

I've never seen the hole in a tsn880 scope body. Is it a bayonet mount or threads? If threads, what is the diameter and pitch?

I have an Optolyth reticle eyepiece. It has m37x.75 threads. (37mm major diameter x .75mm thread pitch).

Or, am I barking up the wrong tree with this idea?

I have a TSN-600 and the eyepiece has a bayonet mount. I'm pretty sure it's the same bayonet throughout all Kowa spotting scopes.

 

[ken226]

Ok. I was looking here for eyepiece interchangeability info.

The Kowa Eyepiece Compatabiliy Thread

I'm putting this on as a definitive guide to what fits on what with Kowa scopes and eyepieces, if anything has been missed or I've got something wrong feel free to post corrections. Hopefully this can serve as a one stop solution to a recurring question. Kowa TS 502 - I'm fairly sure this will...

www.birdforum.net

It looks like the tsn600, tsn660 and tsn1, 2, 3 and 4 share the same eyepiece mount setup.

I'm not sure what the barrel diameter is, but it looks pretty close to an inch.

If I assume those scopes all also share the same 420mm objective focal length, the Burris eyepiece would need to be mounted at an eyepiece focal length of 14mm to have a 30x image and correct reticle subtensions. So, I would have to turn away 1.2333mm of the material in the eyepieces shoulder, and fabricate an adapter, so that it fit 1.2333mm deeper into the Kowa scope body.

 

[Glassaholic]

Ok. I was looking here for eyepiece interchangeability info.

The Kowa Eyepiece Compatabiliy Thread

I'm putting this on as a definitive guide to what fits on what with Kowa scopes and eyepieces, if anything has been missed or I've got something wrong feel free to post corrections. Hopefully this can serve as a one stop solution to a recurring question. Kowa TS 502 - I'm fairly sure this will...

www.birdforum.net

It looks like the tsn600, tsn660 and tsn1, 2, 3 and 4 share the same eyepiece mount setup.

I'm not sure what the barrel diameter is, but it looks pretty close to an inch.

If I assume those scopes all also share the same 420mm objective focal length, the Burris eyepiece would need to be mounted at an eyepiece focal length of 14mm to have a 30x image and correct reticle subtensions. So, I would have to turn away 1.2333mm of the material in the eyepieces shoulder, and fabricate an adapter, so that it fit 1.2333mm deeper into the Kowa scope body.

I love this kind of innovative thinking

 

[ken226]

I'll work on it over the next couple weeks. If I find the idea to be viable, I'll report back to this thread.

 

[JohnK454]

I have a kowa 821m, here's a couple pics of the bayonet mount on the 27x LER eyepiece. The OD of the barrel at the base of the lugs is 1.160". Depth to shoulder is. 374"

 

[ken226]

I have a kowa 821m, here's a couple pics of the bayonet mount on the 27x LER eyepiece. The OD of the barrel at the base of the lugs is 1.160". Depth to shoulder is. 374"View attachment 7244921View attachment 7244922

Me and @Skookum worked on this a little today.

Unfortunately, it's not going to be possible with the Burris eyepiece.

The OD of the Burris barrel at the base of the lugs is about 1.25" and the metal there is very thin.

The inside diameter of the Burris barrel is bigger than the outside diameter of the Kowa barrel.

If anyone is interested, there's a brand new Burris mil eyepiece listed on eBay now?.

A couple years ago 2 hide members, @thewolf and @mike_f verified that the Burris eyepiece does indeed fit the Vortex Razor HD gen 1 85mm spotting scope.

http://www.snipershide.com/shooting/threads/vortex-razor-hd-20-60x85-burris-ranging-reticle.6876136/

And apparently, both the Burris and Vortex gen 1 30x reticle eyepieces also fit the Swarovski ATS/STS ATM//STM spotters as well.

https://www.snipershide.com/shooting/threads/reticle-eyepiece-for-swaro-spotting-scopes.173174/

The Optolyth eyepiece has a 37mm (1.457") barrel diameter. It's huge, and definitely not possible.

 

[99106]

Sorry been tied up with work. The Kowa 500 series is a fixed eyepiece. The 600 is a removable with the 600, 660 & 82SV sharing the same ones. The 770 and and 880s share an eyepiece that is different from the 600 series. I've got an 880 if you want me to measure it. Just tell me where to mic at.

 

[ken226]

Sorry been tied up with work. The Kowa 500 series is a fixed eyepiece. The 600 is a removable with the 600, 660 & 82SV sharing the same ones. The 770 and and 880s share an eyepiece that is different from the 600 series. I've got an 880 if you want me to measure it. Just tell me where to mic at.

Having never seen the mounting setup of the 880, I'm not sure what to ask you to measure.

To determine if this is possible, I would need the inside diameters of the hole in the scope body.

If it's threaded, that would be the minor diameter of the threaded hole.

If it's a bayonet mount, that would be the diameter of the hole that the eyepiece barrel fits into.

Some scopes, like my Optolyth, have several diameters. There is a 37mm threaded hole, about 8mm deep, then further in the diameter reduces to 30mm for another 10mm of depth.

Knowing what diameters, depths, and if threads or bayonet would be helpful.

Also, I'm not confident in the 500mm objective focal length number for the 880. Than number came from an internet forum. I would need to know if that number is accurate.

 

[ifly4vamerica]

I have a couple Kowa's and just emailed my salesguy for that info. Not sure if he will give that out but worth a shot. I also have an extra eyepiece for the 880 that id love to send off to be etched if anybody knows where that may be done. But I'm not even sure if that's possible.

 

[ken226]

I have a couple Kowa's and just emailed my salesguy for that info. Not sure if he will give that out but worth a shot. I also have an extra eyepiece for the 880 that id love to send off to be etched if anybody knows where that may be done. But I'm not even sure if that's possible.

I think it's pretty unlikely you'll be able to find someone who's able and willing to disassemble an eyepiece to etch a lense. The method most likely work would be adapting an existing eyepiece.

The Burris eyepiece barrel is way too big to adapt to the tsn1-4 and tsn600.

But, the tsn880 is a different animal.

I've never seen one, but:

This tsn880 eyepiece adapter adapts 1.25” Astro eyepieces to the tsn880 body.


If I assume that means the id of the hole in this adapter is 1.25", the Burris eyepiece OD or the hole id in this adapter could easily be turned to fit.


It looks like this adapter is designed to thread into the tsn880 body, implying the 880 eyepiece hole has some bigass threads.

The OD threads on this adapter must be about 1.375"

I could easily turn off the lugs on the Burris eyepiece to fit this adapter, or make my own adapter.

 

[ifly4vamerica]

When I get home I will measure the threads on the body and let you know what info I get on the focal length.

 

[ken226]

Also, the 500mm focal length of the 880 means that mounting the Burris eyepiece so that the reticle lense is 1.436mm further from the objective focal point than in the Burris scope body would keep the reticle subtensions accurate.

I drew a .ipt solid model of the Burris eyepiece housing, so I'll have accurate dimensions to reference.




But, the fly in the ointment, is.. The Burris eyepiece I had available to measure for the CAD work was a loaner. I'm not able to machine it, nor do I have a 880 scope available to use for making and fitting a prototype adapter.

So, it's likely all academic. I won't be dropping 2450$ for a spotting scope just to test this idea. I already have a spotter with a reticle.

The barrel diameter at the base of the lugs on this Burris eyepiece is 1.25". The lug major diameter is 1.396". Just behind the lugs there is a shoulder that is 1.407" diameter, then another diameter reduction to 1.341" just before the main shoulder.

 

[ifly4vamerica]

I just got confirmation that 500mm is the focal length. Also was told they have the tremor 4 in the works possibly as an add on between the eyepiece and the body, kinda like their 96x extender. But who knows. If I get a wild hair ill buy a burris and that adapter and send them to you. But like you said, I already have a spotter with a reticle myself. LOL

 

[ken226]

I just got confirmation that 500mm is the focal length. Also was told they have the tremor 4 in the works possibly as an add on between the eyepiece and the body, kinda like their 96x extender. But who knows. If I get a wild hair ill buy a burris and that adapter and send them to you. But like you said, I already have a spotter with a reticle myself. LOL

A Tremor 4 adapter would be awesome, if they actually did it.

Another thought I just had. If those bigass threads in the 880 happen to be m37x.75, the Optolyth eyepiece may just thread right in. The focal length difference would probably result in about a 9% error in subtension accuracy, unless a 1.83mm spacer was placed between the eyepiece and scope body.

If it has m37 threads, the hole should be 35.7mm.

I have the Optolyth eyepiece. It's got a decent reticle, that can be rotated 360° in it's housing.


BH Photo Video sells an 880 1.25" Astro adapter for 30$ that looks like it would be easy to adapt to the Burris eyepiece as well:

 

[wichitaguns]

About a year late to the party. But with the Burris 1.25 barrel, could I mount it to my pentax which accepts standard eyepieces?

 

[Shanej45]

I just found the thread. Very interested

 

[99106]

I just got confirmation that 500mm is the focal length. Also was told they have the tremor 4 in the works possibly as an add on between the eyepiece and the body, kinda like their 96x extender. But who knows. If I get a wild hair ill buy a burris and that adapter and send them to you. But like you said, I already have a spotter with a reticle myself. LOL

Kowa has a tremor adapter in the works?

 

[CoryT]

It would seem like the Burris eyepiece should go into the Pentax PF-80ED. It uses 1.25” Astro eyepieces, so the Burris could be turned down and the rear collar set to act as the stop to get the requIred focal length. I just need to check to see if the 1.25” tube length of .5” or so will let the eyepiece lock in place

 

[Smokin7s]

Never mil dots ever

 

[CoryT]

OK, eyepiece arrived today. Tube is actually 1.2560, so it's a press fit into the Pentax as it stands. Should be no problem to turn it down to 1.250 all the way to the shoulder. At that point there are two questions. What is the datum for the lens focal length and will the Pentax scope have enough travel in the focus system to get to infinity? Pressed in to the lugs you can focus at about 25 yards, so I expect there will be more than enough travel when inserted the rest of the .125 or so that gets to the final shoulder. I've got shims to adjust the focal length that should get me within .0015 of the mathematical value determined above to calibrate the reticle. I'll start cutting the barrel tomorrow and we'll see how it goes.

 

[CoryT]

OK, so it can be cut to fit the Pentax, and there seems to be enough focus travel when placed at the estimated length for the reticle. The 556 class is on the range right now, so calibration will have to wait until this evening or tomorrow AM, but so far so good.

To get it in the chuck I had to take the extending eyecup apart, but that turns out to be just 3 small brass screws and some small rods. It was prettu square though, and centered up inside .0005, which is more that good enough. There is a secondary shoulder on the very back ring not shown in the CAD drawing above. So right now, not having a Burris scope, I can't tell what the stop surface should be. I may need to cut it back more or I may need more shims to extend the length. As I get focus, I presume it's close. I'm going to do a quick comparison to a Leupold spotter and see if it's close.

 

[CoryT]

Pentax owners, rejoice! It's actually within .1 over a 3 mil measurement right now, and actually needs to have the shoulder cut back further, which is good because that will extend the focus travel. I'm going to cut it right back to the main rear ring and then shim as required.

Note that this in on a straight body Pentax PF-80ED, the angled units have and even longer focal length and may prove problematic.

 

[Shanej45]

I think I am getting lost in the sauce.
I have a tsn880.
With and adapter that is 1.436mm further from the objective focal point than in the Burris scope body that the eye piece with modification could work ?