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ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia

Some experience with a few Kowa 663 copies. (1 Viewer)

mskb

Well-known member
Hi Everyone,

I just thought I would share the following experience with the Kowa 663s so that you can check in on some of these points, the next time you are considering a scope. This is by no means a review - I do not think I am qualified enough.

TLDR:
1. I will 100% recommend the K663 for its competitive resolution, colors, CA control, and build quality, and the Kowa company's support.
2. One caveat … I will do so ONLY after you have had a chance to look through it, and when you are absolutely sure you are comfortable looking through it.

I had a chance to check four objective copies and three 20-60X TE-9Z EPs from different sources. The difference between the best and worst performing among these objective-EP combos was no more than a block in the USAF chart. Because I have some doubts about my distance measurements, I would take my measurements ranging from ~116/65 to ~116/61 arc seconds with a grain of salt.

I spent some time star testing these under different conditions, with a good amount of advice from Joachim, Henry & David (thank you all!). If there’s one aberration they all shared, it is astigmatism. All K663 + TE-9Zs just couldn’t shake it off. One copy added slightly excess CA to the mix. One copy added slight coma. Another copy (a 1 year old demo from store) added both pinching and coma. I am still not sure of spherical aberrations so I would rather let an expert chime in when they get a chance. These conclusions were made by relating the realized star test result with the images posted by Henry Link and his descriptions on the subject in various scope/binocular reviews here.

My newb-ness with star tests means I am unable to conclude how severe these effects are relative to the rest of the scope landscape but the “worst” aberrated scope here (the in store demo) beat an ATS65 with their standard zoom and their Swaro wide-angle EP by at least a block in resolution, and an Opticron MM4/60 (perhaps an an apples to oranges comparison here given the objective diameter difference). I guess the ATS was a poor copy.

In addition to the aforementioned optical aberrations & resolution considerations, there were differences in focus wheel smoothness ("buttery smooth" to "stutter-y"), which further contributed to variations in the ease of focus. For terrestrial observations however, I thought one must be real astute to notice a significant difference in resolution across all these scopes when focused on target at reasonable zoom ranges. I agree this is not the same as conclusively saying the scopes are diffraction limited.

Now for the caveat mentioned in TLDR: Where the K663s continue to bother me a lot is in their available ER. I do not wear glasses, and I do not yet 100% believe in Kowa’s ER ~16-16.5mm specifications. My current measurements indicate the ER profile here is like a parabolic curve, started in the neighborhood of the listed ER specification around 20X, falling down rapidly to their lowest to about ~35X and recovering relatively slowly post. Specifically, around 20X and 60X, the scopes would perhaps meet the listed ER specification of ~16mm. By 25X, the ER appears to quickly drop by about 3-4mm, and around ~35X, the ER feels quite narrow for me at ~10-12mm. It then starts going up again slowly. So: I have some serious doubts about the listed 16-16.5mm ER specification here. When I am certain, I will update the thread.

With careful eye positioning, I am finding this ER pattern to not cause too much of an issue. However, if I do not get used to this within a year or so, I would be actively looking for another scope despite its competitive attributes.

I must acknowledge the help from David, Henry, Joachim and Paul Kardos during this process once again.

Cheers, and thank you all,
Kumar
 

marcsantacurz

Well-known member
Sounds like that must have kept you busy for a while comparing all those combinations!

So it sounds like in actual use you're saying that it was hard to detect differences, but in start tests or charts you could see them?

Marc
 

mskb

Well-known member
Hey Marc, how’s it going?! Hope all’s well! Yes, that’s basically all I am saying. :) also that: please check in store if you can before you buy, and that the mechanical bits like focus wheel stutter appear to cause more significant differences in real life (at least with these copies) than their subtle optical aberrations, which mostly died out in 3-5 rings of defocus.
 
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mbb

Well-known member
What a thorough testing!
I should look up info on star testing etc., out of curiosity. I am very happy with the optical quality of my scope based on field use, but still it would be interesting to try such testing. :)

Now for the caveat mentioned in TLDR: Where the K663s continue to bother me a lot is in their available ER. I do not wear glasses, and I do not yet 100% believe in Kowa’s ER ~16-16.5mm specifications. My current measurements indicate the ER profile here is like a parabolic curve, started in the neighborhood of the listed ER specification around 20X, falling down rapidly to their lowest to about ~35X and recovering relatively slowly post. Specifically, around 20X and 60X, the scopes would perhaps meet the listed ER specification of ~16mm. By 25X, the ER appears to quickly drop by about 3-4mm, and around ~35X, the ER feels quite narrow for me at ~10-12mm. It then starts going up again slowly. So: I have some serious doubts about the listed 16-16.5mm ER specification here. When I am certain, I will update the thread.

What you noticed about the eye relief reminded me of something similar I had read somewhere. I have just found the link back: https://tvwg.nl/testrapporten/telescoop/kowa_tsn-773-883.shtml
It is a review (in Dutch) on the website of a birding association in the Netherlands, with also a chart showing what you described about the eye relief changing, compared also to some eyepieces of other brands.
There are some other, interesting and thorough reviews on that website.
 

mskb

Well-known member
Beautiful! Those curves you point out, pretty much recapitulates my observations!

I must thank you for the link @mbb. First, it is quite reassuring to have some added confidence on the aforementioned results. I didn't have much confidence at all to trust the setup I had, without having an expert check it at least once. Second, the author presents his ER curves across various key scope models. This is very good as it gives us a general sense of the landscape; otherwise one might constantly wonder if other models might improve over the ER issue mentioned above.

For star testing, I would recommend starting with Henry's reviews on a few scopes and follow the links and discussions from there. Godspeed! :)

Cheers,
Kumar
 
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mskb

Well-known member
Some images at 60X.

As I find the ergonomics improving with more usage, here are a few sample shots at 60X TE-9Z at various distances in the order of their distance, shot with an iPhoneX and a GoSky phone adapter. All the images have been resized to 1600px long dimension.

Notice, the eyes resolved more detail & 3d like experience of the views than the phone - just to say that one might not be wrong to expect at least this level of sharpness from the K663s at 60X with a TE-9Z 20-60.

1. the light pole: ~875ft / ~292 yards / ~266.7m
2. Corner of a building in twilight: ~1700ft / 566 yards/ ~518.16mt
3. Prudential tower in twilight : ~3.4miles /17952ft/5984yards/5471m
4. The flag pole : don't know the distance. Should be farther than (3). At arm's length, the exposed portion of the flag pole measured about ~6cm. On a less hazy day, all the stars in the flag were captured by the phone image.

In some images, lack of a perfect phone-fit & phone-focus causes some blur asymmetry in the corners.

Thanks again to Joachim for all his helpful thoughts and insights.
 

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Taxboy

Well-known member
What a thorough testing!

I should look up info on star testing etc., out of curiosity. I am very happy with the optical quality of my scope based on field use, but still it would be interesting to try such testing. :)







What you noticed about the eye relief reminded me of something similar I had read somewhere. I have just found the link back: https://tvwg.nl/testrapporten/telescoop/kowa_tsn-773-883.shtml

It is a review (in Dutch) on the website of a birding association in the Netherlands, with also a chart showing what you described about the eye relief changing, compared also to some eyepieces of other brands.

There are some other, interesting and thorough reviews on that website.
Beware of going down the rabbit hole. I did this with a previous TV; my eyes were happy with the picture but a digital test suggested some minor defects. From that point on it always was at the back of my mind when viewing. Just my thoughts YMMV
 

mbb

Well-known member
Beware of going down the rabbit hole. I did this with a previous TV; my eyes were happy with the picture but a digital test suggested some minor defects. From that point on it always was at the back of my mind when viewing. Just my thoughts YMMV

Good point!
I think this is also the big issue with these forums in general: they are a treasure of information with many very helpful enthousiastic people sharing common interests, but you risk ending up wanting to upgrade wondering if what you have is OK rather than enjoying it... I think I already spend way too much time here reading |>|
It happens I still haven’t further looked up info about the star tests or tried them out. Maybe that is a good thing ;)
My biggest complain about my scope appears to be the limited use it gets lately, mainly with a lot of other stuff to do getting priority, but also with my binoculars being easier to just take with me on unplanned, little walks or biking moments... I have even been wondering if a cheaper scope wouldn’t give me more fun just due to the fact of not worrying as much about it for carrying on the bike. However, when watching a bird through it, or even the moon now and than, aaaahhhh.... what a joy it can be from such a view (thanks to both the tremendous optics and subject) :)
 
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ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
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