Why not more DIY “big eyes”?

[Brian Fahs]

A couple weeks ago I purchased a mint set of twin 664s with the adams adapters bracket .

I was like everyone else wondering just how good these could be. I never owned the btx but do own swaro 15x56 hds and a kowa 884. I have owned and sold swaro sts80 and sts65. I love my swaro binoculars and own several sets. Kowa rocks in the spotter world IMO.

I would like to thank Hatchet Jack, Esau, and Adam botcamp on here for answering all my questions and concerns. I know i wore them out but they kept assuring me how good they are.

For my limited use so far I am very impressed. No disappointments whatsoever. I would recommend the adapter bracket I have. Well built and designed for sure. The size and weight of the setup work well on most descent tripods and heads.

This setup takes the whole glass with both eyes to another level. My 15s are not as clear , bright, or powerful to my eyes. The 30x wa eyepiece is just unreal good. I want to experiment with digiscoping on this setup. I could see it replacing my 884 as I seldom use it on highest magnification.

I had been contemplating the 774 twin setup with the 35x eyepiece. I have no doubt it is even better but size , weight and required tripod and head size make it unlikely to carry far from the truck. I feel the twin 664 with 30x wa eyepieces is a phenomenal hunting optic.

 

[SikaSeeker]

I'm curious about the twin 664 vs. BTX as well.

I have read that you need the 95 or 115 to match the twin 664 for light transmission. I forgot where. Maybe at MM or CW forums.

I also wonder how much 3D effect you get with the twin 664. Or is that only at close range.

To answer query , in theory

Big eye 2x 66mm =68.42 cm.squared total aperture area

85BTX = 56.75

95 BTX = 70.88

115 BTX = 103.87

So the 664 Big eye should outperform the BTX85 and be around level of BTX95.

It would be very interesting to compare against the BTX115 , I’d bet the difference isn’t that huge.

Hatchet Jack said they can hang with Highlanders that have 105.62.

 

[Brian Fahs]

I forgot to add the field of view and edge to edge clarity of the twin 664 with 30x wa eyepiece is incredible.

 

[SikaSeeker]

Few pics from a Japanese friend of a friend. As I’ve been looking for another 664 I ended up with two old 613, I’ll give one to nephew. Had bit of fun attempting to align them on one tripod plate but unfortunately they’re a smidge off. If I removed the hood it *might* work. The straight version could be mounted like the Nikon scopes in the picture. The grey ones are Sony Branded Nikon built scopes.

 

[SikaSeeker]

I queried an astronomer about this topic. Thought I’d share here, he’s a proper expert & commissioned enormous 18 inch(!) binoscope made from two Newtonian reflectors. His YouTube is “astronomy drawings” and he welcomes anyone to his home in rural Italy to have a go!

His response

“ The 115mm also has superior resolution. But... the binos have a smaller exit pupil, allowing for lower power and so the two would offer a completely different experience. The 66mm binos would behave like a good 66mm pair of binoculars with the possibility of higher power. Excellent for cruising the Milky Way and retaining the joy and immersion of obser6with both eyes. The 115mm would rather be an excellent planetary scope (supposing it's an APO) but with a binoviewer it would suffer from significant light loss. It all depends on the binoviewer and the object in question, but I expect it would still slightly outperform the 66mm if the binoviewer is of high quality and with sufficient aperture. Still, no binoviewer can match the "feeling" of a binoscope, nor can it take 22mm Naglers, for example”

Food for thought.

Personally I’ve purchased a Kowa 664 body from Japan today so waiting delivery & then making a bracket begins.






Reply

 

[SikaSeeker]

Holy Moses that was fast. DHL Express picked up in Fukushima, Japan on Wednesday, two days later it’s in Ireland.

Now to get to work getting a bracket

 

[OspreyZB]

Following. I have a couple Nikon fieldscopes I would like to try this with, this off season. Looking forward to seeing what you come up with @SikaSeeker.

 

[SikaSeeker]

Posted more pics in another relevant thread by mistake. One thing I learned is it’s actually fairly simple, the trick is having a setup strong enough to stay collimated when being jostled around. That’s the main reason for CNC billet aluminium setups etc, and probably what you need if you want something that is solid & looks nice.

There’s a set of Adams Kowa 664 dual spotters on fleabay right now FYI.

 

[SikaSeeker]

Ended up with two more Kowa scopes, both 82mm. One is the 824 (red ring flourite) the other the 822(non flourite). They were reasonable money so couldn’t pass them up & I wanted to see for myself the difference between Highlander 82mm and 64mm using two eyes.

I’ll look out for another 824 then try and compare vs the 664 setup. Also posted comparison pics of both front elements so you can see the difference. The LED head torch I used was perfect. It shows the extra glass layer used in the flourite, so you can see extra reflections/layers. I’ve seen people do this with green lasers when buying Astro telescopes to try and figure out if it’s a doublet or triplet design.

 

[willfrye027]

I would love to see someone try to make the new swaro 56mm scope into a set of big eyes. They are small enough that I could see it replacing 15s at low power and the BTX at higher power in some circumstances. The BTX is a great optic but 30x is pretty specialized and it would be nice to have the option to zoom in a bit beyond that for field judging

 

[BBob]

I would love to see someone try to make the new swaro 56mm scope into a set of big eyes. They are small enough that I could see it replacing 15s at low power and the BTX at higher power in some circumstances. The BTX is a great optic but 30x is pretty specialized and it would be nice to have the option to zoom in a bit beyond that for field judging

The problem I see is the STC is a straight design without a prism offset so the minimum IPD would be fairly large and might not work for a lot of people. Same goes for the ATC. You’d have to build a horizontally adjustable bracket to adjust the IPD. With the two commonly used brackets (Adams, Wells) you rotate the scopes to adjust IPD which is simpler to build. You’d need to find the max OD off one of the scopes to figure out what the minimum IPD would be to see if it’s even worth trying. This is why the Swaro X series aren’t used, the oculars are too big and you can’t get the minimum IPD down small enough to use them.

 

[willfrye027]

The problem I see is the STC is a straight design without a prism offset so the minimum IPD would be fairly large and might not work for a lot of people. Same goes for the ATC. You’d have to build a horizontally adjustable bracket to adjust the IPD. With the two commonly used brackets (Adams, Wells) you rotate the scopes to adjust IPD which is simpler to build. You’d need to find the max OD off one of the scopes to figure out what the minimum IPD would be to see if it’s even worth trying. This is why the Swaro X series aren’t used, the oculars are too big and you can’t get the minimum IPD down small enough to use them.

I’ll probably stick with my btx 85 until someone else figures it out!

 

[SikaSeeker]

In an earlier post I shared pics from a guy in Japan who has turned various brands of scopes into big eyes and all had the offset prism. The 82mm Kowa’s have them. Ironically, the angled Swaro STC looks to have a similar design as the Nikon ED82 Schmidt prism that’s deeply(&cleverly) recessed into the tripod Mount area to streamline the design. *that’s just my impression I don’t know for a fact*

Will, have you tried the twin Kowa 664 or would that be too heavy for you? Another complication is sample quality, one of my 664s is clearly superior in some way. Just an amazing scope for its size.

The 82mm Kowa will accept the Baader MK IV (~$250) zoom on the external thread so you could have a poor man’s Highlander with zoom function (that’s one angle I’m working on atm).

The other is to make adapters for Astro eyepieces, Kowa don’t offer low power eyepieces unfortunately. 30x and 50x (and 1.6x magnifier).

 

[Antares]

Not a DIY setup, but I have a pair of 884s and Adam (of Adam's Adapters) is making me a bracket for them. Should have it in the next month. I can't wait. As far as Kowas go, I think these are as big as you can go and still get a usable PD. The new 99S and 88S are both too big, from what I've heard.

I've got two wide-angle, fixed 35x eyepieces and two 1.6x extenders, which will give me the option of making them 56x. I'm pumped. They're beautiful to look through singly, so I can't wait for the pair. Sometime in the next few months I'll take them to Haleakala for some star viewing... probably a fair bit of deer viewing as well.

 

[SikaSeeker]

That’s the ultimate set up. Would like to see a detailed comparison of the Kowa wide angle zoom and how much you lose on field of view versus fixed. The magnifier just seems clunky system. Maybe it’s worth it for FOV, less light loss than zoom possibly.

 

[willfrye027]

In an earlier post I shared pics from a guy in Japan who has turned various brands of scopes into big eyes and all had the offset prism. The 82mm Kowa’s have them. Ironically, the angled Swaro STC looks to have a similar design as the Nikon ED82 Schmidt prism that’s deeply(&cleverly) recessed into the tripod Mount area to streamline the design. *that’s just my impression I don’t know for a fact*

Will, have you tried the twin Kowa 664 or would that be too heavy for you? Another complication is sample quality, one of my 664s is clearly superior in some way. Just an amazing scope for its size.

The 82mm Kowa will accept the Baader MK IV (~$250) zoom on the external thread so you could have a poor man’s Highlander with zoom function (that’s one angle I’m working on atm).

The other is to make adapters for Astro eyepieces, Kowa don’t offer low power eyepieces unfortunately. 30x and 50x (and 1.6x magnifier).

I’ve looked through hatchet jacks pair. They were nice. Didn’t compare side by side with my BTX which I bought a while later. I do some pretty long/steep hikes and don’t want anything more heavy or bulky than the btx at this point which was why the 56 swaro was interesting for a big eyes setup with a little more versatility

 

[Antares]

That’s the ultimate set up. Would like to see a detailed comparison of the Kowa wide angle zoom and how much you lose on field of view versus fixed. The magnifier just seems clunky system. Maybe it’s worth it for FOV, less light loss than zoom possibly.

Yes, I agree. Not sure what the benefits are of the fixed eyepiece + extender vs. the variable eyepiece. I have one of the 25-60x variable eyepieces too. I haven't gotten a chance to extensively compare them side-by-side yet, but at first blush the fixed 35x doesn't seem spectacularly brighter, or wider. If I found a good deal on another 25-60x eyepieces I'd probably buy it just so I could try all the possible eyepiece/extender combinations. I'm just playing around to see what I like best. I'm am interested to try the extender on the fixed 35x eyepieces though. We've had a terrible spring for viewing weather, foggy, rainy, misty... so I haven't gotten to play around as much as I would've liked.

 

[Gone4Days]

Too heavy.

 

[Antares]

Too heavy.

What's too heavy?

 

[Gone4Days]

What's too heavy?

Topic title: “Why not more DIY “big eyes”?

Too heavy to carry around