773 versus 883 scopes (1 Viewer)

773 (second-best scope?) versus 883 (best scope?)

I asked this question at the end of another thread, but I decided it deserved its own thread. I am not able to get a look through a 773 Kowa prominar, but the fact that it is 6.7 ounces lighter and about 18% cheaper than the 883 has me strongly considering it. The only review I could find of the 773 describes it as the second-best scope out there (second only to the 883/884). See the link here:

http://www.optics4birding.com/kowa-tsn-773-spotting-scope-review.aspx

It says it is better than the other 80-82 millimeter scopes out there. I compared the 883 to the Swarovski 80 HD, and did not see a big difference in terms of brightness; so I am thinking there is not that much of a difference between the 773 and 883 either.

Anyway, for those who have knowledge of the two or have looked through them, will I regret going for the 773 rather than the 883 in terms of image quality, e.g. resolution at 60x? One thing that is important is I will be using it mostly for birding, and possibly a little digiscoping. And carrying it on some multi-mile hikes.

Thanks,
Jim

Need to decide by Monday, so any help would be appreciated.

Jim

I have looked through both, and in fact tested both, although of the 773 I have seen only one sample which was probably slightly sub-par as judged by star-testing results.

If you can afford it, I recommend the 883. The 883 is slightly better than the other 80-85mm scopes, while the 773 I feel is certainly very good, but not quite the "second-best." Also, since they share the same body, and the balancing has been designed to work with the 883, the 773 is rear-heavy and not as convenient on a tripod. This is a nuisance especially when digiscoping. 14% difference in theoretical (and practical) maximum resolution due to larger aperture is not insignificant either.

Kimmo

Thanks for sharing your experience and expertise Kimmo! I will go with the 883 as you suggest. At least for me, the weight and price differences are not significant enough to tip the balance the other way given the other factors you mention.

Best wishes,
Jim

Just wanted to follow up on this thread since I imagine others are facing the same decision. I actually decided to go with the 773 after all. I decided I was not going to do any digiscoping, preferred the lighter weight, and was uncomfortable paying over $2000 for a scope (esp. when you can get great scopes like the little kowa and big zeiss for under 2k!). (With the money saved I purchased a Panasonic ultra-zoom digital camera).

I think the 773 is quite nice, bright, and at 60X quite sharp and reasonably bright, which is the main thing I was looking for. I have not compared it side by side with the 883, but it seems comparable. I still wonder whether things might look a little better through the 883, but if I had bought the 883, I would be wondering about the other things I could have done with the money, and whether I would be more comfortable lugging the lighter 773 around. I have also found that, at least in my neck of the woods, atmospheric distortion, i.e. heat waves, are often severe enough that the high optical quality of the 773 or 883 does not really help much. This seems especially so when viewing waterfowl at fairly long distances (even during winter). That's another reason not to go overboard paying for optical quality--esp. if your not digiscoping.

Jim

J. Moore said:

Just wanted to follow up on this thread since I imagine others are facing the same decision. I actually decided to go with the 773 after all. I decided I was not going to do any digiscoping, preferred the lighter weight, and was uncomfortable paying over $2000 for a scope (esp. when you can get great scopes like the little kowa and big zeiss for under 2k!). (With the money saved I purchased a Panasonic ultra-zoom digital camera).

I think the 773 is quite nice, bright, and at 60X quite sharp and reasonably bright, which is the main thing I was looking for. I have not compared it side by side with the 883, but it seems comparable. I still wonder whether things might look a little better through the 883, but if I had bought the 883, I would be wondering about the other things I could have done with the money, and whether I would be more comfortable lugging the lighter 773 around. I have also found that, at least in my neck of the woods, atmospheric distortion, i.e. heat waves, are often severe enough that the high optical quality of the 773 or 883 does not really help much. This seems especially so when viewing waterfowl at fairly long distances (even during winter). That's another reason not to go overboard paying for optical quality--esp. if your not digiscoping.

Jim

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Thanks, Jim, for bringing up this topic and following through with it. From the paucity of responses, I conclude that the Kowa still has not really caught on? As anyone going for either of those apparently superb models should certainly try to gain some insight on the alternative as well. Aside from those other brands, of course.

Kimmo, thanks for your input here as well! On the Leica thread you say you don't expect the new Leicas to come up to the performance of the 883. I assume you conclude this from the design? Or what makes you come up with your advance expectations?

Robert,

My preliminary assessment questioning the potential of the upcoming Leica to challenge the performance of the Kowa 883 is quite simply based on the following. Having seen and tested the Kowa, my conclusion is that the design and execution of the 883 is sufficiently good (low overall aberrations, very low CA, high contrast and light transmission) that it comes as close as any birding scope design I have yet evaluated (and closer than most) for approaching diffraction-limited performance for its aperture. Since the Leica gives up about 7% in aperture, it simply cannot equal the resolution and brightness potential of the bigger Kowa. This is not pure theory either, since I was able to directly compare one sample of the Kowa 883 to an 82mm scope specimen which, based on both star- and resolution-testing, does have diffraction-limited performance. The Kowa was slightly but undeniably better.

Now, when it comes to which scope a birder should get, the Leica or the Kowa, the answer is not so simple. I have not seen the 25-50x zoom eyepiece yet, and that is in my opinion the true innovation of the new Leica scopes. Although personally I don't think I would be willing to settle for 50x as the highest magnification I could easily use, the idea of having wide-angle to super-wide angle views instantly available throughout that magnification range is very appealing.

Kimmo

Kimmo

What resolution test do you use? Not had a chance recently to look at any of the new Kowas (or for that matter the Swarovski, Nikon or Zeiss larger models in any real detail) so can't comment on which ones may achieve diffraction limited performance. I note that Zeiss have a converter that allows 1.25" push-fit eyepieces to be used with their scopes. This is useful. Do you have something similar that can be used with the Kowas? If so then you can push the power up to judge resolution.
If we assume that the manufacturers are designing their scopes to have optimum correction at infinity, then regardless of whether these scopes are to be used for birding or not, the resolution tests should ideally be carried out on targets at infinity. The moon is (believe it or not) an extremely useful target for this type of test. It contains very bright and dark boundaries for judging contrast and secondary spectrum, some very small but visible detail made of both bright and dark spots, thin lines, faint low contrast markings on crater floors. Avoid the full moon, its too low contrast. Magnifications of 100X + will give quite a good idea of what resolution levels are reached with any scope.
If we want to test scopes for diffraction limited performance then we have to remove potential issues like close focus SA (or even not-so-close focus, if the correction is poor), and avoid the boiling gases that make up daylit air. If a telescope is designed to a tolerance of maximum of 1/4 wave (worse error on the wavefront), then the testing conditions need to allow us to see that. Daylight atmosphere is a problem, even when it appears calm and apparently free from heat shimmer. Indoor testing or outdoor testing at short distances during the day is useful but not ultimately accurate for assessing resolution and contrast testing. The results may show a similarity to those from a target at infinity, but also may not.


andytyle

Thanks Kimmo - I'd missed the Leica 25-50 zoom. I agree it looks very appealing on paper - 41m FOV for 25X at 1000m beats my Swarovski 20-60 zoom with 36m at 20x. I'd happily give up the extra magnification at the top end in exchange for a wider view at the bottom end. My Swarovski zoom always annoys me every time I look through it at 20X. I always think the FOV is poor for £1500, even though I know it's par for the course, and I wouldn't settle for a fixed eyepiece. The black ring round the view that makes it look like you are looking down a drinking straw makes it worse. If the new Leica scope matches the Swarovski for weight and compactness my Swarovski will be going !

Mark

I think someone should start a topic on Zoom eyepieces in general, regardless of brand. My last one goes 16x-49x. It is OK, but with zooms, something is always not exactly what you want.

Andy,

Since Kimmo and I use similar methods for resolution testing I think I can get the ball rolling here. We both use the USAF 1951 Resolution test Pattern. It's a lp/mm bar target. I have it in various forms; vacumn deposited chromium on glass and printed on plastic and paper. I use three test set-ups. One is indoors, 10m and illuminated by a Solux 4700K halogen lamp. Two are outside, one is about 32m and the other about 60m. I always have a reference scope of known quality set up next to the test scope so I can evaluate the quality of the test conditions and my own eyesight. I do most resolution testing of scopes at 32m. For any birding scope that distance is beyond Suiter's recommendation of 40 times the focal length of an APO refractor to avoid "an erroneous estimate of spherical aberration". Using the USAF target I can expect my reference telescopes (Takahashi and Astro-Physics APOs) to yield resolution in arcseconds of around 120/D with D being the aperture of the scope in mm. Applying the same standard to a birding scope set up next to the refrence scope seldom produces resolution any better than 140/D and usually worse. If a birding scope needs more than 60x to see its resolution I use 5mm and 4mm astronomical eyepieces.

Henry

Henry

OK thanks. So do most if not all of the spotting scopes you test yield results that are less than the theoretical resolution for that aperture? Your Astrophysics and Tak (Sky 90 or 102)? perform to the limit, but not the spotting scopes even when you use a 4mm eyepiece?

andytyle

Thanks, Henry, for saving me time by rolling the ball first.

My method is basically the same as Henry's, except that usually I use the bar targets only at the short distance, which for me is just under 11 meters. I'm fully aware that this is shorter than would be required for fully accurate readings, but I have found that in practice it is good enough in almost all cases. Indoor testing avoids the problems of unsteady air and unreliable light conditions. In addition to the resolution charts Henry has, I use a bar target made by Jan Meijerink (which has line patterns in four orientations, not just two, and is thus better for evaluating astigmatism), a non-standard lower-contrast target and an artificial star. The latter allows me to compare star-test results of SA between the "too short" distance I have indoors with what I see outdoors, either using real stars or glitter points during daytime. I also utilize a 3x12 Zeiss Classic monocular as a booster behind the eyepieces of the scopes, which gives me magnifications up to 180x with most scopes, and 225x with Nikons. Thus I can get high-enough magnifications with any scope, irrespective of the eyepiece selection or mounting system. The moon is a fine target, but the problem is that it is not reliably available for viewing when needed. As you said, it ideally needs to be much less than full, but for me here in the north the problem is having both clear skies and steady air when I need them. When the moon is visible and the air is clear, it is easy enough to immediately see which of two scopes aimed at it is better, but quantifying that meaningfully is not quite so easy.

Now, to answer Andy's last question for my part, most birding scope specimen I have tested indeed fall way short of diffraction-limited performance for their aperture. What is worse still, the design or make of the scope is usually not the determining factor, but "luck of the draw" in getting a good sample. Henry's estimations of average performance in the post above are, I think, overall about right in light of my own experience as well, although I have probably tested a larger number of birding scopes, so I have chanced to come across more that have been very good samples. Actually, If you'd like to take a look at a pretty good indication of real quality spread, check Jan Meijerink's tests of six Zeiss and six Kowa scopes on the www.tvwg.nl site. Of the ones he shows, my guess is that only his old Kowa 823 would be diffraction-limited.

Average samples show enough errors such as astigmatism, pinching or miscollimation to make the spherical correction error caused by the short distance just about irrelevant. To emphasize this point, I am yet to see a situation where a scope that tested below expectations at the 11m distance would have been noticeably better at 1km-infinity distances. When the day comes that I am forced to increase the distance in order to compare top birding scopes and find the winner among two candidates, I'll be very happy indeed, since that would truly mean that a major step forward has been achieved in quality control.

I have never had access to reference scopes as good as Henry's, but my current reference scope does indeed resolve about 120/D, shows almost no spherical aberration in star-tests, and is (on a good day - collimation in this scope can sometimes get off very slightly, giving less than fully concentric ring patterns very close to focus) nearly free of other aberrations as well.

Kimmo

andytyle said:

Henry

OK thanks. So do most if not all of the spotting scopes you test yield results that are less than the theoretical resolution for that aperture? Your Astrophysics and Tak (Sky 90 or 102)? perform to the limit, but not the spotting scopes even when you use a 4mm eyepiece?

andytyle

Click to expand...

I've yet to test a birding scope that reached the theoretical resolution for its aperture no matter how high the magnification is pushed, but I know there are a few cherries lurking out there, like Kimmo's scope. I haven't bought a birding scope yet because I'm still hoping to find one of those. My Tak scopes are FC-50, FS-78 and Sky-90. The Sky-90 is not as good as the others so I don't use it as a reference. Most of the time I use the AP Stowaway, sometimes stopped down to match the aperture of the scope being tested.

Henry

Henry and Kimmo

So, none of the tested spotting scopes (refracting scopes) are diffraction limited. If we attempt, in the new year, to star test a variety of spotting scopes to discover what the common problems are, we can put together a report that can be presented, in a general way, to manufacturers - as a sort-of "come on guys what about a bit of improvement", but mainly as a guide to birders who read this forum, and perhaps even to set up a rudimentary test method for those who are interested.

To begin with, can I ask Henry or Kimmo to provide me with images of extra-focal star images with their scopes (either with a digiscoping method for spotting scopes, and/or a webcam in the case of the Taks.). If you want to proceed with this we can send private emails between us. I also have some images I did in a mock-up home artificial star set-up which I can send.

Henry. I remember the 50mm Tak, and am familiar with the 78mm Tak as well (probably the best small scope they made). The Sky 90 suffers sometimes from collimation slip, and can also have a little 3rd order SA. The star images will show this.
I had for a while, an FS60C which I used for terrestrial use and casual astronomy. The first one I bought had about 1/4 wavefront error of lower order SA, and was returned for a replacement. The second one was better. Can I recommend the use of an accessory called the Extender-Q with the Sky 90. It can transform the performance of all Tak short f/ doublets. I wouldn't describe the FS60C or Sky 90 as apochromatic without the addition of the Extender-Q.

andytyle

Andy,

I afraid I can't make or post photos. Maybe after we buy a new computer, which should be soon. Our current one uses vacumn tubes. ;-)

Yes, the Extender-Q is essential with the SKY-90. It took me three tries to get one as good as I have now (the first one was as unfocusable as the HST), but I still wouldn't have kept the third one if the importer hadn't sent along an Extender-Q for me to try. That kept me happy until AP notified me that I would be granted the priviledge to send them a large sum of money for a Stowaway.

Henry

Comments on high end spotting scopes

Henry may remember my comments regarding an evaluation of several Leica Televid 77 apo's. The best of the lot had a near perfect star test and could be used effectively at approx. 160x. My testing methods parallel those of Henry and Kimmo although I am not as actively involved in testing as I used to be. The Leica scopes had an even wider variation than the Zeiss 85 FL's. My approximation for the worst was 1/2 wavefront and the best, 1/8 wavefront. A technician at Leica actually told me that their wavefront spec minimum was indeed 1/2 wave. If they had bumped this up to 1/4 wave which would have significantly improved its definition at higher powers, they would have had to reject about half of their scopes (based on my limited sample).

I applaud Kowa for what seems to be superior fabrication and assembly techniques resulting in a consistently higher quality product such as the 883. Hopefully Zeiss, Leica and other high end manufacturers will endeavor to improve as well but I wouldn't count on it - 95 percent of the public at large still doesn't know the difference. It's easier (and less costly) to field a few complaints from time to time than to change your fabrication techniques or quality control standards.

I agree that even the best spotting scopes I have seen are not quite as good as a fine astronomical telescope. However, a spotting scope such as the 883 likely comes close enough to be very enjoyable and is generally speaking much more compact, waterproof and field worthy than its astronomical counterpart. - Herb

P.S.: A little off subject: If a true astronomical quality 45degree correct image diagonal were to become available Henry's dream of a perfect spotting scope might be realized, especially if this were produced in a 2" variant. Such a diagonal coupled to one of Henry's fine scopes would be superb and the full range of astronomical accessories would be available (think Paragon, Ethos and Binoviewer :t: ). The current versions of these diagonals leave much to be desired.

kabsetz said:

..... Kowa, my conclusion is that the design and execution of the 883 is sufficiently good (low overall aberrations, very low CA, high contrast and light transmission) that it comes as close as any birding scope design I have yet evaluated (and closer than most) for approaching diffraction-limited performance for its aperture. Since the Leica gives up about 7% in aperture, it simply cannot equal the resolution and brightness potential of the bigger Kowa. This is not pure theory either, since I was able to directly compare one sample of the Kowa 883 to an 82mm scope specimen which, based on both star- and resolution-testing, does have diffraction-limited performance. The Kowa was slightly but undeniably better.

Now, when it comes to which scope a birder should get, the Leica or the Kowa, the answer is not so simple. I have not seen the 25-50x zoom eyepiece yet, and that is in my opinion the true innovation of the new Leica scopes. Although personally I don't think I would be willing to settle for 50x as the highest magnification I could easily use, the idea of having wide-angle to super-wide angle views instantly available throughout that magnification range is very appealing.

Kimmo

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Thanks Kimmo for this clarification. It will be interesting to see how much the practical evaluation will correspond with the theory. Or rather, whether there might be aspects that offset the inherent quality differences. (Assuming Leica get it right regarding manufacturing consistencies, in the first place.)

Personally, I rarely go beyond 50x, but it is always a welcome option to have 60x available.

Quote: 'P.S.: A little off subject: If a true astronomical quality 45degree correct image diagonal were to become available Henry's dream of a perfect spotting scope might be realized, especially if this were produced in a 2" variant. Such a diagonal coupled to one of Henry's fine scopes would be superb and the full range of astronomical accessories would be available (think Paragon, Ethos and Binoviewer ). The current versions of these diagonals leave much to be desired'.

In the UK, our much-revered Horace Dall made some very neat 90 and 45 degree prisms. I had one once that I used with a simple 80mm doublet refractor and an internal Televue barlow that I used as a spotting scope in the 80's. Excellent image. Much better than the Kowas and Optolyths at the time.

I remember when the William Optics 2" 45 degree prism diagonal came out a few years ago. Much was said about it, but the reality was a let down.....as usual. Looked great but lowered resolution and contrast a little. Amici and roof prisms are notorious for lowering image quality, unless they are made with zero tolerance for error. Roof prisms in the higher quality bins like Leica, Zeiss etc tend to be accurate, more so than many porros in average quality porro binoculars.....simply because they have to be, to avoid introducing astigmatism because of the footprints of incident beams. VERY flat porro prisms are the best (most economic) way to achieve astigmatism-free images in prismatic binoculars.

For spotting scopes, the ideal is a diagonal mirror which is truly flat, and simply putting up with the reversed image. Similarly you can tip the mirror a little more so that the eyepiece sits at 45 degrees, but you need to make sure the flat mirror is very flat. Not difficult, just take one from a good quality Newtonian. I'm pretty sure Televue did (or still do) a 1.25" version of a tipped flat. Many of the very expensive 2" star diagonals used in astronomy are not actually that flat, regardless of what the manufacturers say. It doesn't really matter though, as long as these flats are used as star diagonals, i.e. placed near focus, they won't affect the image quality much.

andytyle

field testing 773 versus 883

Swissboy said:

From the paucity of responses, I conclude that the Kowa still has not really caught on?

Click to expand...

I think you are correct Robert. I had been researching spotting scopes on the Internet off and on for two weeks or so, and it was only when, almost by chance, I stumbled upon the thread on this forum discussing the new Kowa scopes that I learned there was a "new king". If no one else gets around to it, I think I will post a review of the new scopes in the equipment review section of this forum. That may help spread the word better among the less regular participants on this forum.

On a related matter I am somewhat reluctant to confess that I actually ended up exchanging my 773 for an 883. It was mostly for psychological reasons. I was not dissatisfied with the 773, but could not rid myself of the nagging doubt that the 883 might provide somewhat better views.

Since some have contacted me off forum about these scopes, I wanted to give my further impressions. Though I have not compared them side by side, and my impressions should thus be taken with a grain of salt, I think the 883 does provide, in my non-expert opinion, slightly but noticeably brighter, more contrasty, and sharper views at 60X. They are good enough that about the only powers I use on the zoom are 20x (to locate something) and 60x (to get a close look). I did not feel this way when using the 773.

On the downside, the 883 is noticeably heavier than the 773. So much so that when I first received it, I was strongly leaning towards returning it to get my 773 back. (Though it should be noted that the 883 weighs about 64 ounces with eyepiece, which is quite reasonable for a full sized scope -- and considerably lighter than the big Pentax, for example). But after carrying the 883 in the field I found the extra weight is not that much of a burden, and did not make me reluctant to carry the scope around on extended walks (though I have decided I now need foam cushions on my tripod!). However, it was not balanced well when carrying on my shoulder, because of my light (4.1 pounds) tripod. So I will probably have to get a heavier tripod, which means still more weight to lug around. :-(

In any event, both scopes are very appealing choices, though neither one quite perfect.

Jim