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Old Thursday 6th July 2017, 20:59   #26
Gijs van Ginkel
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Steve O4B, post 25
Pure fluorite crystal is very vulnerable and can in fact not be used on surfaces exposed to open air, so the producer has to take precations to avoid that.
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Old Thursday 6th July 2017, 21:21   #27
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Gijs,

What you say about the maker needing to know what they are doing is true. However, Kowa has been making scopes with pure fluorite crystal since the TSN3/4 introduced in the 1980s, and their track record is excellent. They certainly know how to make the fluorite last. I have not heard of any problems with Kowa fluorite scopes that would be resulting from the choice of lens material.

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Old Thursday 6th July 2017, 21:33   #28
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The Kowa 553 (inc the zoom eyepiece..not inchangeable) will be slightly more expensive than the ATS 65+25-50x around here.
Weight 810 grams (vs 1400g for the ATS), but Kowa body made of polycarbonate. FOV 44-23 (15-45x).
Just wonder why Kowa choose to put the cheapo zoom on it, as the Prominar series is know for their huge AFOV EP:s...a bit sad.

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Old Thursday 6th July 2017, 21:33   #29
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Hi,

Kowa fluorite lenses are made by Canon-Optron, the same division of Canon which does the fluorite work for Takahashi - and unlike Kowa they even have refractors with fluorite in the front element (FS series) - not a problem with the right coatings.

The real question is if fluorite is needed in this instruments and at the magnifications offered by the fixed EP or if visually perfect CA control could be reached too with sth like FPL-53, FCD-100 or OK4.
My guess is no due to the small aperture, without having fired up OSLO...

Joachim
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Old Friday 7th July 2017, 03:04   #30
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Quote:
Originally Posted by kabsetz View Post
Gijs,

What you say about the maker needing to know what they are doing is true. However, Kowa has been making scopes with pure fluorite crystal since the TSN3/4 introduced in the 1980s, and their track record is excellent. They certainly know how to make the fluorite last. I have not heard of any problems with Kowa fluorite scopes that would be resulting from the choice of lens material.

Kimmo
Kimmo, The first scopes to ever have pure fluorite crystal are the TSN-883/884. The TSN-3/4 and the TSN-823/824 had some variety of calcium fluoride doped glass.

OTOH, the TSN-883/884 have been around for 10 years without the crystal being an issue. So, you're right in that respect.
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Old Friday 7th July 2017, 03:15   #31
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All ED glass is not created equal. There are many different versions of ED glass. many of the lower cost optics with ED glass don't have fluoride in any of its several versions. Compare a Nikon Monarch 5 with a Zeiss Victory SF. That said, the Kowa TSN-550 series scopes don't have ED glass. They have pure fluorite crystal objectives. This is not glass that is melted into blanks and then ground, it is crystal that is grown, then ground. The Celestron Hummingbird ED is at the low end of ED glass. The Kowa TSN-553/554 are at the extreme top. You're comparing Yugos with Ferraris
I agree with all your points except that based on the quoted specs, the Celestron is fully competitive in FoV and eye relief.
It is at least a high performance Yugo versus a detuned Ferrari Dino for 5x the price.
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Old Friday 7th July 2017, 07:27   #32
jring
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Kimmo, The first scopes to ever have pure fluorite crystal are the TSN-883/884. The TSN-3/4 and the TSN-823/824 had some variety of calcium fluoride doped glass.
I beg to disagree - the first spotting scopes with with fluorite crystal were the TSN-3/4 introduced in 1986. Takahashi first produced an astro scope with fluorite in 1972 - the TS 80.

They certainly didn't use some variety of calcium fluorite doped glass aka ED glass as these were not available back then. They were developed later to replace the expensive and difficult to work with CaF2 crystal (although FPL-53 is not a lot better to work with).

You can easily check if a scope uses fluorite crystal or ED glass by shining a green laser through it. With a fluorite element, you will see reflections where the beam enters and exits the crystal and nothing in between, while with glass you see a distinct line between the entry and exit point. This line is caused by the light being scattered by bubbles in the glass, which are absent in crystal.

Joachim

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Old Friday 7th July 2017, 16:10   #33
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It is disappointing that KOWA has cut corners by using plastic body and poor quality zoom lens, yet the priced in premium range. I own Takahashi refractors with Fluroite, some of their 4inch scopes FC series with back fluorite element can be purchased for less than $2k.
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Old Wednesday 12th July 2017, 03:05   #34
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We received both the TSN-501 and TSN-553 samples today. I didn't spend much time with the 501, but did a fair amount of comparison between the 553 and other scopes.

Our first test pitched the Opticron MM3 50mm with SDL v2 eyepiece. The difference was beyond astounding. Since UPS got here around noon, long distance viewing was fraught with heat shimmer. We concentrated on holes in the hedge across the parking lot. The Opticron could barely see into the hole, but the 553 saw nearly to the far side of the hedge. The 553 also had significantly better contrast. Cell phone photos bore this out.

Later in the day, I compared the 553 with the original version of the Vortex Razor 16-48x65. Again, the 553 was brighter, sharper, and had better contrast. I didn't take any photos of this comparison due to time constraints.

These are preliminary observations. I'll have more to post next week. I plan on taking the 553 birding on Saturday morning.
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Old Wednesday 12th July 2017, 16:12   #35
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Dear Steve.

How does the Kowa 553 compare to the well regarded Nikon 50mm?

I don't have the Nikon, but have thought of getting one.

Are the weights similar?
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Old Wednesday 12th July 2017, 16:37   #36
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Dear Steve.

How does the Kowa 553 compare to the well regarded Nikon 50mm?

I don't have the Nikon, but have thought of getting one.

Are the weights similar?
The Opticron MM3 and MM4 are better than the Nikon. If you want something in the $800 range, get the Opticron. But, neither come close to the Kowa TSN-553.
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Old Wednesday 12th July 2017, 16:55   #37
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The Opticron MM3 and MM4 are better than the Nikon. If you want something in the $800 range, get the Opticron. But, neither come close to the Kowa TSN-553.
No way is the MM3 50 better than the Nikon ED50 good samples of both. Come to think of it I haven't star tested a really good MM3 yet. Each to their own though.
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Old Wednesday 12th July 2017, 18:48   #38
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What I want is a good Canon 50mm image stabilized scope that is steady at 50x hand held. Maybe a straight through design not angled.

If anyone says this isn't possible, I would say that Canon has the necessary technology now to make it.
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Old Wednesday 12th July 2017, 20:06   #39
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We received both the TSN-501 and TSN-553 samples today. I didn't spend much time with the 501, but did a fair amount of comparison between the 553 and other scopes.

Our first test pitched the Opticron MM3 50mm with SDL v2 eyepiece. The difference was beyond astounding. Since UPS got here around noon, long distance viewing was fraught with heat shimmer. We concentrated on holes in the hedge across the parking lot. The Opticron could barely see into the hole, but the 553 saw nearly to the far side of the hedge. The 553 also had significantly better contrast. Cell phone photos bore this out.

Later in the day, I compared the 553 with the original version of the Vortex Razor 16-48x65. Again, the 553 was brighter, sharper, and had better contrast. I didn't take any photos of this comparison due to time constraints.

These are preliminary observations. I'll have more to post next week. I plan on taking the 553 birding on Saturday morning.
How's the FOV and eye relief?
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Old Thursday 13th July 2017, 23:33   #40
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.
Yes, it's fairly fast at f5.5 but on the other hand it's only 55mm aperture...

Joachim
If my calculations are good the scope is actually f/6.5..grants 15x-45x ,like most 60-65 scopes, thus having 360mm FL ..divided between 55mm aperture..6.54....makes even less necessary to use fluorite..and perhaps the celestron uses low grade ed glass,but if its performance is good,then it was well designed..I dont know what glass the Nikon ED50 uses,but works great correcting CA in a quite fast F/5.7 scope.(I dont think the MM3 is better than the Nikon either,to me feels flimpsy and Image quality is on par at best.).
So the Nikon does not come even close to the Kowa 553?..Is it better then than the 883..?..because the Nikon comes close to that level of performance,at least reasonably for its size and price pooint---.in any case,It,the kowa, seems extravagant for what we are used in THIS forum ...perhaps the market is totally different and the lil kowa becomes a hot item..If it would have used the big wide zoom,then perhaps,even at a hig price it would have appealed to 88 users as a travel companion..as it is, I dont have any interest personally,and I think people wanting a really expensive travel scope would find the Swaro ATX 65 a more interesting option..That is if Swaro does not release a 55 module and makes the kowa look even worst

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Old Friday 14th July 2017, 01:28   #41
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I may eat my words, but totally agree with mayoayo.
As currently described, the scope seems an odd hybrid, a superior objective lens coupled with an ordinary zoom in a plastic body, priced at a huge premium.
Perhaps the expectation is that scope prices will increase dramatically, something that Nikon was earlier seeking to achieve with their EDG series.
If the 883 successor model is priced at $4000+, the 553 begins to appear reasonable. No idea whether the Chinese competition will allow that.
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Old Friday 14th July 2017, 07:54   #42
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If my calculations are good the scope is actually f/6.5..grants 15x-45x ,like most 60-65 scopes, thus having 360mm FL ..divided between 55mm aperture..6.54....
Hi,

if we assume that the zoom on the 553/4 is actually the small body zoom (which the image showing it labeled 60x linked by me somewhere above in this thread implies), the calculation is as follows:

The small body scopes (except for the odd 82SV) all have a focal length of 420mm and the small body zoom yields 20-60x on those - which makes it a 7-21mm zoom.

So if this zoom is used in the 553/4 and gives 15-45, we get 7x45 or 21x15 = 315mm as the focal length of the 550 bodies. So the focal ratio is 315mm/55mm = 5.7...

A 55m doublet with fluorite at that focal ratio should show very good CA control - maybe better than is needed for 45x...

But why oh why did they use that zoom... sure, the magnification range of 15-37x with the big body zoom would look a bit strange, but then they could have increased the focal length of the body a bit to 380mm and it would have been roughly 19-45x... that would have made the objective f6.9 and any FPL-51 clone ED glass would have given great results too to bring down the price.
I'm quite sure they could have kept this one below 1000g and a bit longer than it's now and it would have been quite a bit more attractive.

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Old Friday 14th July 2017, 09:01   #43
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Using the old zoom will keep development costs down. That it's not exchangeable is a bit annoying though, especially if you already own that zoom EP. Don't doubt that 553 will be the best small scope optically, but still it's just 55mm, limiting brightness and resolution, and raw light transmission have never been Kowas strength.

Cost/mm objective lens will be less than for the Kowa 88mm + EP though.

Wealthy travelers might buy this, but you still need to carry a tripod and head if you want the same versatility/stability as a larger scope.
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Old Friday 14th July 2017, 10:16   #44
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Using the old zoom will keep development costs down.
As would using the wide angle zoom from the 880 series...

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Old Friday 14th July 2017, 14:15   #45
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There was a well regarded Vixen 55mm telescope, possibly fluorite objective.

The manufacturing cost of telescopes, at least astro telescopes, varies between the square and cube of the aperture, not linearly with aperture.
I don't know what the factor is nowadays, as giant scopes seem remarkably cheap, mainly due to computerisation, I suppose, and advanced altazimuth mounts.

P.S.
The Vixen 55mm fluorite is possibly the same as the Celestron C-55F. Made by Vixen?
Said to be the same as Takahashi FC-50.
But if from 1985 I would be wary, in case moisture has affected the fluorite.
Maybe f/8 440mm focal length.

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Old Friday 14th July 2017, 16:01   #46
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:

The small body scopes (except for the odd 82SV) all have a focal length of 420mm and the small body zoom yields 20-60x on those - which makes it a 7-21mm zoom.



Joachim
I stand corrected..I didnt realize the small zoom true focal lenght,until you pointed to it..It grants 21-63X in the 82SV,and I assume that scope has 450mm,like the 823..in any case 315 mm seems right for a 55 mm scope of that size..
Couldn´t they have designed the scope with a removable eyepiece at least?
I guess they want you to buy their narrow view zoom at a very high price yes or yes..
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Old Friday 14th July 2017, 16:21   #47
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There was a well regarded Vixen 55mm telescope, possibly fluorite objective.

The manufacturing cost of telescopes, at least astro telescopes, varies between the square and cube of the aperture, not linearly with aperture.
I don't know what the factor is nowadays, as giant scopes seem remarkably cheap, mainly due to computerisation, I suppose, and advanced altazimuth mounts.

P.S.
The Vixen 55mm fluorite is possibly the same as the Celestron C-55F. Made by Vixen?
Said to be the same as Takahashi FC-50.
But if from 1985 I would be wary, in case moisture has affected the fluorite.
Maybe f/8 440mm focal length.
Hi,

yes, the Vixen FL55S f8 - built until 1984... not quite the same as the FC-50 but close...

SInce all of these are in Steinheil configuration aka fluorite element to the back, I would not be too concerned - I have two old Kowa 77mm objectives which are probably from late 80s or early 90s and they're fine.

Joachim
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Old Friday 14th July 2017, 16:56   #48
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As would using the wide angle zoom from the 880 series...

Joachim
The price is already unrealistic IMO.
The smaller zoom is probably a better match, mechanically.

New video, Paul Hackett using it on a monopod:

http://www.kowaproducts.com/Kowa-TSN...potting-Scope/

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Old Friday 14th July 2017, 19:25   #49
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The video contains a short animation which shows some blurry interior detains. My reading is that the prism system is a Porro followed by a semi-pentaprism with focusing accomplished by prism movement. The objective elements are not revealed, so it may be a triplet or more likely a simple doublet.

The last images in the video seem to suggest that this scope is a shrunken TSN-883. That is something of a misrepresentation, given how different the optical designs are. The 883 uses a 5 element objective (including a doublet focusing lens), a Schmidt erecting prism and a more sophisticated zoom eyepiece.. The design of the 553 looks to be much closer to a shrunken TSN-3 from 30 years ago.
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Old Saturday 15th July 2017, 20:14   #50
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I found this Japanese video review of the TSN-553.

https://www.youtube.com/watch?v=pJxMFAsyKII

The reviewer voices some of the same complaints that have been aired here, including the insupportably high price. He confirms that the prism configuration is Porro + semi-pentaprism and also mentions that Kowa has not specified what mirror coating material is used in the semi-pentaprism.
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