Story of two Kowa Prominar 883 scopes (1 Viewer)

Hi to all,

after I made a deal with the seller that I can test the sample and have the right to return if it's proven optically bad one, I ordered Kowa Prominar 883 + 25-60x zoom eyepiece.

I star tested the first sample right away when it was arrived and quickly concluded that it had pronounced miscollimation and also noticeable astigmatism. If I compare the results to these two specimens Henry Link has tested in this thread: https://www.birdforum.net/showthread.php?t=125302 , I can say that the amount of miscollimation was clearly even greater in this sample than that of the worse sample of Henry's test. About astigmatism I would say that it was roughly the same amount also, very noticeable. I'm by all means not an expert on interpreting star testing results but anyway spherical aberration looked to me to be corrected quite well; at least the outside focus showed quite clear inner rings with not overly bright outer ring and the overall pattern looked quite the same on both sides of sharp focus (of course except 90 degree opposite oval shapes caused by astigmatism).

I compared this sample of Kowa to Zeiss Victory Diascope 85 (good or very good sample) on a daylight just by trying to read small text over a distance. Judging byt the star test, I didn't expect the Kowa to be at the same level at all and that just was the case; Diascope was way sharper and had better contrast. Focusing the Kowa was difficult because it was hard to find the sharpest point and it felt that it was impossible to get it really sharp. When just looking any objects with Kowa it felt the image was somehow not relaxed and not completely sharp. So it was obvious that this sample had to go back.

So I got another sample and when I conducted star test with that one, I for my relief saw perfect collimation and zero (or at least minimum) amount of astigmatism. The outside focus pattern looked quite good but I think the first sample was little better in this regard; at least the inner circles were harder to see clearly in this second sample. At this point I was already quite sure this sample was a keeper. It looked even better than the other sample in Henry's test because there was not the same amount of astigmatism and collimation looked perfect but on the other hand, maybe the correction for SA was little worse. I think the Zeiss Diascope had also better correction for SA than this sample of Kowa 883. But as said; I'm not an expert and I'm not totally confident when judging the amount of SA, at least in these small marginals.

Next I compared it with Zeiss Diascope and they had quite similar performance reading different sized text over a distance. Both have great sharpness and especially contrast.

I have earlier compared Zeiss Diascope85 to my Leica Apo televid82 and found the Zeiss to be better in terms of sharpness and contrast as well as brightness. In brightness the Kowa seems to be at about the same level as Zeiss Diascope and similarly better than my Leica.

After these comparisons I was convinced that this would be my next scope so I bought it and as it seemed to be that good, I also bought the 1.6x extender.

Today I compared my Leica with it's own 1.8x extender next to my new Kowa and 1.6X extender and the sharpness, contrast and brightness were markedly better with Kowa and I was very, very impressed how well the Kowa kept small details when zooming in. I think that in a decent atmospheric circumstances the Kowa will be perfectly usable with the extender all the way to 96x mag. One can not say the same thing with my Leica as it gives more resolution about up to 70x magnification but behind that image deteriorates too much in many ways. Maybe Leica's extender works just fine but the scope itself has both astigmatism and a lot of spherical aberration (the outside pattern is nowhere near looking same than the inside pattern), so it can not get all the benefit possible with the extender. Had the Leica been very good sample, I would probably not have replaced it ever; in every other respects it's still a great scope. Besides I can tell that the first Kowa I tested was clearly worse than my Leica also and third sample of Kowa 883 which I tested next to my Leica (just by looking different objects outdoors) last summer, was maybe even worse than this bad sample of Kowa 883. But the time I bought my Leica, I wasn't aware of these sample variations among even "alpha"brands and how to (star)test them and so I got not that good specimen. My bad...

So overall I think my worries with scopes are pretty much over for a good while as I have this, maybe not *perfect*, but at least very good sample of Kowa 883 and excellent 25-60x zoom eyepiece + the 1.6x extender.

Juhani

Hi Juhani,

great to hear you now got a keeper! And thank you very much for this post - I'll certainly quote it in the future as an example for how to buy a scope the right way!

Joachim

jring said:

And thank you very much for this post - I'll certainly quote it in the future as an example for how to buy a scope the right way!

Click to expand...

Well Joachim, you were one of those whose posts I read from various threads here in Birdforum and became aware of these things, so I should thank you and many others who have shared their knowledge and experience on this subject.

So thank you Joachim (and others) very, very much!

It should be that everyone would be aware these sample variations and how to test them and so be able to demand quality, which high end expensive scopes should offer to everyone who buys them. I just can't understand why so bad scopes have left the factory, if it weren't so that tolerances are so wide and they expect folks will be satisfied with those very poor samples. Maybe it will be that way, until everyone can tell that some samples are optically defective.

Best regards,

Juhani

Sample variation is something that is often mentioned regarding spotting scopes, what is not clear though is the cause and the fix.

Can anyone enlighten me on this.

giosblue said:

Sample variation is something that is often mentioned regarding spotting scopes, what is not clear though is the cause and the fix.

Can anyone enlighten me on this.

Click to expand...

My view:

The cause: insufficient quality control (and this is also the case with the very best).

The cure: improving quality control.

A long as I can get a Leica Ultravid 8x42 out of the box that exhibits uneven focussing between the two tubes - something immediately visible -, I consider the nice signed quality control note that accompanies the binocular as not worth the paper that it is written on (I am generally a big Leica fan).

Other quality issues, such as the ones described by Juhani, may be less obvious and less easy to detect, but they are quality issues nevertheless, and they would be preventable, but maybe at a cost not considered economical by the producer.

Canip

Thanks Juhani! :t:
Now that you have seen "the light" and have 2 scopes (so can continue to go birding with just one...), your example can be even more educational if you will send your Leica to repair and let us know of the result...o
I think you now understand when I say that, when needed, my X95 gain with the use of the 1,7x extender that show much more detail up to 120x.

Canip said:

My view:

The cause: insufficient quality control (and this is also the case with the very best).

The cure: improving quality control.

A long as I can get a Leica Ultravid 8x42 out of the box that exhibits uneven focussing between the two tubes - something immediately visible -, I consider the nice signed quality control note that accompanies the binocular as not worth the paper that it is written on (I am generally a big Leica fan).

Other quality issues, such as the ones described by Juhani, may be less obvious and less easy to detect, but they are quality issues nevertheless, and they would be preventable, but maybe at a cost not considered economical by the producer.

Canip

Click to expand...

Insufficient quality control simply reflects an inadequate manufacturing process.
When the US auto makers began to build Rolls Royce Merlin engines during WW2, they were frustrated by the loose artisanal standards provided, which were inadequate for good QC without expert technicians tuning each one. So the design standards were tightened up for mass production.
Sadly, production of scopes and binoculars remains an artisanal activity, with annual production in the thousands rather than million, so quality has to be inspected in rather than being built in. Any solution will have to come from outside the current industry. Perhaps hopefully someday Apple will develop a need to offer scope like optics....

etudiant said:

....
....
....
Perhaps hopefully someday Apple will develop a need to offer scope like optics....

Click to expand...

An iScope Air? Or an iBino Pro?

Yes, faulty control somewhere down the line, but where?
And what would needed the fix them?
Is it he actual glass that's at fault, the way it's cemented in, adjustment?
What I'm asking is, if you sent back to Kowa, could they fix it, or is it scrap?
Baader turn thousands possibly 100s 1000s of their Hyperion zooms made in China and nobody seems to have a problem with them.

DRodrigues said:

Thanks Juhani! :t:
Now that you have seen "the light" and have 2 scopes (so can continue to go birding with just one...), your example can be even more educational if you will send your Leica to repair and let us know of the result...o
I think you now understand when I say that, when needed, my X95 gain with the use of the 1,7x extender that show much more detail up to 120x.

Click to expand...

Actually tomorrow I maybe have just one scope left (well, I also have Kowa 601...) because Leica goes to my friend who is ready to sort of buying it. We have been birding together many many times and he has looked through my Leica quite amount and he has for years been asking if I will sometime get another scope, then he can buy my Leica. If he wants, I will sent it to repair and we'll see what happens and then he can think the deal again. It's up to him, otherwise I may not see the extra trouble to send it to repair at least just now. I will show him how to star test and he can see the difference between my Leica and Kowa and judge them side by side. After all, my Leica falls in the category between this good sample of Kowa 883 and the first bad sample of Kowa 883 judging by the sharpness and contrast, both Kowas were brighter of course.

Couple of my friends have ATX95 but none of them have the extender, I would be really interested to look through that combination in good viewing conditions...If the scope is good sample, I'm sure it will be able to resolve smaller details than my Kowa because of bigger aperture.

Juhani

giosblue said:

Yes, faulty control somewhere down the line, but where?
And what would needed the fix them?
Is it he actual glass that's at fault, the way it's cemented in, adjustment?
What I'm asking is, if you sent back to Kowa, could they fix it, or is it scrap?
Baader turn thousands possibly 100s 1000s of their Hyperion zooms made in China and nobody seems to have a problem with them.

Click to expand...

Hi,

that is unfortunately difficult to determine. Except for cementing as this doesn't happen with spotting scope objectives.

For a refractor objective to work well, it has to be competently designed, then the elements need to be ground and polished exactly as the design prescribed and after that, the elements need to be mounted in an objective cell - and this is kinda tricky, as you don't want them to move in any direction or rotate but on the other hand "nice and tight" will introduce astigmatism aka pinching.

That being said, if the design is sound it can be fixed, so he could send his other scope (which happens to be a Leica, the not so great Kowa was returned) to Portugal and it probably can be fixed. In some cases the fix might mean to replace the objective lens though, as Leica probably will not have a master optician hand-retouch the bad one.

Joachim

The magnifications used by birdwatchers with scopes is very low. 40x, maybe 60x.

The eyes are usually not looking for the finest detail in normal observations.

The bird may be moving, so fine detail is anyway not seen.

Poor scopes can provide quite adequate observations.

This even applies to astro scopes.
I wrote a paper a long time ago on observations with numerous astro scopes, most of which were not the best quality. Yet the observations were good as long as one understands the faults and limitations.

There is a difference in my mind to testing scopes and actually using them.

Very few observations need highest quality scopes.
Planetary scopes do need to be high quality, but even here useful observations are made with moderately good scopes.

Top quality spotting scopes should at least be well aligned when leaving the factory, but they could get knocked out of alignment if they are dropped in transit.

The times when Schneider or Zeiss final quality control had a hammer and just smashed sub performing camera lenses and threw them in the rubbish bin are probably long gone.

The average punter doesn't appreciate top quality. The name suffices even if the scope or binocular is substandard.

For me I just look at a bright star and within 30 seconds I know if the scope is acceptable Then the much more stringent test of looking at Jupiter at high power sorts out the good from the very good.

B.

Binastro said:

The magnifications used by birdwatchers with scopes is very low. 40x, maybe 60x.

The eyes are usually not looking for the finest detail in normal observations.

For me I just look at a bright star and within 30 seconds I know if the scope is acceptable Then the much more stringent test of looking at Jupiter at high power sorts out the good from the very good.

B.

Click to expand...

You make it clear that spotting scopes remain very useful even if optically deficient.
That said, it would be wonderful if your 30 second star test procedure was adapted by the alpha manufacturers.
Most of us believe still that when we splash out for an alpha, we get at least 'good', with a chance of 'very good'.
It is very disappointing to find out different. :C

At least where I bird, birders frequently use their scopes to the max. A typical situation would be viewing in the early morning or early evening from a bird-tower over some mudflats or an expanse of water and a shoreline, where small stints would be feeding, and distance could be anything from under 100 meters to well over half a kilometre. Often, there is very little if any thermal disturbance in the air, and the scope is the limiting factor. With my diffraction-limited ATX 95, I frequently use the extender and mags above 90x, to distinct advantage.

Also, since aberration effects on image quality deterioration accumulate, and as thermal instability and poor seeing are forms of aberration, a better scope is better also in poor seeing, not only in good seeing. Now that Juhani has two scopes of different aberration levels, he has a nice chance to see what the difference is when seeing conditions are sub-optimal. I strongly suggest trying this out, since the experience is illuminating.

Eyepieces are much, much less critical as far as quality control/image quality (especially resolving power and contrast) is concerned. This also, blessedly, applies to the extenders that Swaro and Kowa use. It is easy for me to see quality differences between just about any two scope bodies/objectives, but when I have tried to cherry-pick eyepieces or extenders, I have struggled to detect almost any image quality differences between them.

- Kimmo

Binastro said:

The magnifications used by birdwatchers with scopes is very low. 40x, maybe 60x.

The eyes are usually not looking for the finest detail in normal observations.

The bird may be moving, so fine detail is anyway not seen.

Poor scopes can provide quite adequate observations.

Click to expand...

That may be true but only partly. In my use I quite often use maximum magnification (50x with Leica) and often would like to have even much more mag.

Very distant (larger species) birds don't move so fast in the image circle and so with the scope that resolves better, you can pull more detail for ID. Often the bigger problem is strong wind causing shaking. Thats typical situation for me that I find bird (tiny speck moving) with my 10x binoculars and then I ID it with scope using max. mag., if air conditions are favourable.

Last night I viewed (~half) moon with Kowa and extender. I have never seen anything like that, Leica with the extender falls far, far behind of that sharpness, contrast and brightness. The air was little turbulent but the surface details were so crisp that for a good while I had a big smile on my face...

But anyway, yesterday afternoon I compared my Leica and Kowa and in a very bright sunlight behind our back, momentarily Leica seemed to resolve some bird feather details even better than Kowa; as if Kowas contrast and brightness would have been too good for those circumstances! I think the main difference between image of Leica and Kowa is particularly in the contrast, which the Leica lacks with max. mags. (lower mags. the contrast definitely is there). There is no problem of finding the sharpest focus point with Leica, it snaps very easily but the image just lacks the final contrast; as if there was thin grey fog layer forming between the scope and target when zooming in.

My friend first looked through Leica and wowed how good it was. After looking through Kowa he said that he can barely understand how the image can get even more better than Leica's. It's not a big difference but you can see it if you compare them side by side. I think that difference was just mainly due to the optical imperfecties of Leica and if there would have been equally good samples, I think there would have been no detectable differences between those scopes. Well the Kowa would obviously have been brighter due to the bigger aperture.

But had I bought the ~2500€ Kowa + the ~300€ extender only to find that the scope has so bad optical flaws, that it can't get the full potential with the extender, the fact that the image with 40x mag. would have been just "ok" wouldn't have comforted me at all...The first sample I tested, was for me unacceptable but maybe someone else would have think that thats the way good Kowa scope should perform and would have been happy with it. I just couldn't be.

Juhani

PS. So after comparison my friend bought my Leica, I still gave him even couple of months to make the final decision if he finds the Leica to be too bad. We also did star tests for both of the scopes and I expalained the differences between scope diffraction patterns with my tremendous (5 scopes...) practical experience on the subject...Too bad I anymore didn't have the first bad Kowa sample because now we didn't have any scope which could show in a star test what miscollimation looks like...

kabsetz said:

Now that Juhani has two scopes of different aberration levels, he has a nice chance to see what the difference is when seeing conditions are sub-optimal. I strongly suggest trying this out, since the experience is illuminating.

Click to expand...

Well, now I don't have Leica anymore, see my former post...

But I will get lots of chances to do that comparison in the future.

By the way Kimmo, your posts here in Birdforum and reviews on magazines etc. were among the most valuable sources of information. Thank you.

Juhani

Incredibly frustrating. I'm in the process of buying 884s and it is a real hassle having to do final QC myself by buying multiple copies to compare. Hopefully retailers will rebel from the hassle of doing returns and demand the manufacturers clean up their act.