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Anyone tried Kasai 3x50?

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#1 Zavijava


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Posted 18 August 2021 - 01:00 PM

There was a thread earlier this year when these were only available from amazon.jp. Now that Agena sells them, has anyone tried how they compare to Orion and Vixen?

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#2 Astrojensen


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Posted 18 August 2021 - 01:29 PM

I, too, am interested in knowing. 



Clear skies!

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#3 petert913


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Posted 18 August 2021 - 01:51 PM

I've looked through a pair.  They really give you an "oh Wow!" moment..... for a moment.   But I wouldn't pay $150 for them.  Kind of a novelty.

#4 PEterW



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Posted 18 August 2021 - 03:47 PM

How do they compare to the 2x, more/less wow?

#5 MT4



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Posted 18 August 2021 - 08:14 PM

I have the Kasai 2x54.  I've heard it described as being identical to the Orion 2x54, branding aside.   It's a Wow moment the first time I used it,  Very sharp and well-made.  Unfortunately for my local skies it's a novelty only.


I don't know about Kasai 3x50.

#6 Enkidu


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Posted 26 September 2021 - 04:23 AM

I had the opportunity to test these. They offer a unique view if you're willing to tolerate some severe optical compromises.


Haptics and build quality seem pretty nice. Good case. Metal hinge and focusers, mostly plastic barrels that seem black or at least dark gray inside. Flashlight reveals 7 reflections, usually tinted green. Some japanese reviews lamented the lack of eye lens caps, but you really have to clean them between each use anyway! Weight 290g.


There is something uniquely nice about 3x. These definitely go deeper than my DIY 2x54 TC-E2s, and almost reach my 5x25 VisionKings. However, the 5x25s appear quite dark by comparison; I initially suspected the exit pupil, but had the same result in daytime (I found myself wanting to remove the plastic windows in front of the objectives for the first time). Another possibility is that the image brightness in the 3x50s is excellent.


My incredibly subjective impression is that these still give a naked eye feeling, whereas 5x25s (or greater) do not.


Regarding the glass: my best suggestion is to press them to your eyes, look straight ahead and focus on the sky instead of the optics. The flaws are not really noticeable to me that way, and it felt like ~10-12˚ of true field is easy to view, stars crisp and sky background true to life.


That said, the AFOV is 45-48˚ and I get close to 70˚ from my 2x54s. The sweet spot is 1/3rd of the radius and there is a visible 'ring' where the image starts to degrade. Edge of field brightness occurs outside of the sweet spot. By area, 90% of the image is flawed.


I'm not too particular about these sorts of things, the field is probably worse than any gear I have (when I pay attention to it). Perhaps it's a design or manufacturing flaw, or some physical limit that keeps most Galileans near 2x. If these were half the cost, I would recommend them much more enthusiastically. For die hard naked eye observers and fans of low mag views, they’re worth considering.

Edited by Enkidu, 26 September 2021 - 07:32 AM.

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#7 ECP M42



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Posted 27 September 2021 - 12:20 AM

Thanks Enkidu, I was really curious to read an opinion a little more detailed like yours.
What is holding me back is the 48° vision which is narrow. And if the field of view is really 12° max, I already have a 7x32 with 14 ° that makes heads spin. But in fact 3x without prisms, they are also very interesting for the brightness.
I also have a pair of 3,5x and 6x Galileians that make shoes for all the prisms I have, as a transmittance, but the field of view is really frustrating.


There is something uniquely nice about 3x. These definitely go deeper ...

There is nothing more to add! Binoculars are designed and built to magnify. Is the magnification the main function of all optical instruments such as binoculars, monoculars, telescopes, viewfinders, etc.
They serve to increase our ocular abilities. And in this case, 3x is the minimum level to be able, for example, to separate a double star that still appears single to the naked eye. And it is precisely for this reason that the step from the naked eye (1x) at 3x is so different than at 2x. The upper level after 3x is therefore 9x and this is the first level of visibility of those details that are not even perceptible to the naked eye. Another world again! 



#8 Pinac


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Posted 05 December 2021 - 12:06 PM

I could finally get hold of a Kasai 3x50 and am now waiting for better weather to test them.

The image shows in the front row from left:


- Kasai 3x50, 17 degrees, 297g
- Vixen SG 2.1x42, 26 degrees, 430 g*
- Scopetech (AstroHutech) Hinode 1.8x40, 24 degrees, 204 g


In the back row from left:


- Orion 2x54, 36 degrees, 410 g
- Kasai 2.3x40, 28 degrees, 265 g


*there is also a Vixen “clone” from Omegon with 26 degrees, not shown here


Initial impression of the 3x50:

I support Enkidu’s post #6 of 26 September 2021. These 3x50 go definitely deeper than the ones with magnifications around 2x.

Ever since I began using starfield binoculars a few years ago – starting with the original Kasai 2.3x40, later using Vixen SG 2.1x42, AstroHutech 1.8x40 and finally the very wide Orion 2x54 – I felt a bit “underwhelmed” by what could be achieved with these little instruments. Yes, being able to see entire constellations at once was great, but the gain of less than 2 magnitudes over the naked eye didn’t really satisfy me much, and I thought 3x or 4x might bring clearly more.

The 3x50 IS a clear step ahead in this respect, about 2.5 magnitudes can be gained, however this comes at the price of a clearly smaller field of view, particularly when compared with the Vixen or even more the Orion. But I currently believe that I will be happy to trade field of view against a deeper view on the night sky (to be verified).

Enkidu was not too enthusiastic about the optical quality (quote: “By area, 90% of the image is flawed”). My initial impression is not that bad, esp. compared to some of the other widefield binos. But I can’t really say yet. To be followed.


Attached Thumbnails

  • IMG_9038-1.jpg

Edited by Pinac, 05 December 2021 - 12:08 PM.

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#9 ihf



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Posted 05 December 2021 - 12:20 PM

Down at 17 degrees the VisionKing 5x25 starts waking up, paying attention, getting excited and wanting to join the party with their 15 degrees. Mhh. Just noticed there is also the Veber Prima 5x20. Lightweight 265g but only 10.5 degrees.

Edited by ihf, 05 December 2021 - 12:21 PM.

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#10 Enkidu


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Posted 05 December 2021 - 04:18 PM

Thanks for the impressions Pinac. This is a rough instrument, but I find myself using it more and more.


Alpheratz and Matar fit simultaneously in my peripheral view, so these seem to go above spec (~19˚). It's easy to observe 10-12˚.


A good friend (whose opinion is probably more well informed) had success controlling edge of field brightness by cupping his hands around the objectives. I haven't had much luck with that so far.


Mr. Kasai told the 3x50 cannot be mounted in WideBino goggles, though I expect some of you might make it work with some tweaks.


The objective housing of the 3x50s are a good fit for 2" filters without an adapter. The size is so close that it may be affected by temperature…


I have (much) less testing experience than Pinac, and look forward to his evaluation.

Edited by Enkidu, 06 December 2021 - 12:48 PM.

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#11 Pinac


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Posted 05 January 2022 - 11:19 AM

Coming back to what I wrote in post # 8, I had to reconsider my initial opinion in a number of respects, after some limited use of the Kasai 3x50 (for weeks, night sky conditions have been very unfavorable here).


1) Higher mag vs. wider FOV:

I had said that "I believe that I will be happy to trade field of view against a deeper view on the night sky". Well, I am not so sure anymore.
My statement was based on the assumption that, gaining at least between 0.5 and 1 magnitudes when compared to one of the 2x starfield binoculars, I would find that gain significant enough so that I would not miss the "lost" FOV that I get e.g. in the Vixen 2.1x42 or even more so in the Orion 2x54. I now believe that the increase from 2x to 3x is not sufficient - the Kasai 3x50 seems "neither this nor that" to me on the night sky, neither a real bino showing me A LOT MORE objects on the night sky over the naked eye, nor a true widefield device such as the Orion. For instance, the Pleiades look as meagre in the Kasai as in any of the 2x, 2.1x or 2.3x devices. No real brilliance there for me. Same for the Orion - in the 2x binos, I can at least see much more of the constellation than in the Kasai 3x50, so I have at least the widefield effect; I don't have that in the Kasai, and I don't get much of anything else as compensation for the "loss" of FOV.

I think I will be happy to sacrifice FOV if the magnification is at least 4x or 5x - see remarks below re the Visionking 5x25.


2) Image quality:
Enkidu mentioned in post # 6 that "By area, 90% of the image is flawed", and I said in post # 8 that my first impression was more positive.
Comparing the Kasai 3x50 to it "competitors", esp. the Orion 2x54, I have to agree with Enkidu. Esp. when panning, the quite small sweet spot in the Kasai becomes evident. Depending on the way you use your starfield bino, this is more or less of a nuisance. But I find the image in the Orion clearly better corrected than in the Kasai, despite the Orion's much wider FOV.

Also, build quality of the Kasai does not appear to match that of the Orion, nor that of the Vixen or Omegon. The smaller Kasai 2.3x40 had a double central hinge, the larger and heavier 3x50 a single hinge, which I find less than ideal for stability. Of course, the Kasai 3x50 costs clearly less than the Orion or the Omegon and much less than the Vixen.


So to tentatively sum up my current thinking: before I reviewed the Kasai 3x50, I found the Orion 2x54 the most impressive of all the low mag widefield binos. After reviewing the Kasai, the Orion still holds my top spot. For me, "3x isn't enough".



I only recently came across the VisionKing 5x25, which many of the CN members seem to have been using and discussing since a while (see ihf's post # 9 above). Not an ultra-widefield starfield bino such as Vixen, Kasai & Co., but for me, despite the narrower FOV, the better option for sweeping the night sky thanks to the 5x magnification. Having to choose between the Kasai 3x50 and the VisionKing 5x25, I go for the latter.


See mini impression here:



fwiw Pinac

Edited by Pinac, 05 January 2022 - 11:30 AM.

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