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New user and "new" Kowa TSN3 (1 Viewer)

Luca1970

Member
Italy
I greet everyone, I am a new member of this forum, although I know I have been following for a while despite the difficulties with the English language, fortunately there is a google translator.

I love nature of which I am a keen observer and poor photographer.

First of all, I have to thank many visitors to this site for guiding me in the purchase of my new spotting scope, the Kowa TSN 3 (one of the latest versions with protective glass) that I took to support my fellow observers the Kowa TS613. I knew right away that the zoom eyepiece was to be replaced with the newer TSE-Z9B due to the loss of definition and CA over 40x, at the moment I'm waiting to be able to try the new zoom before buying it definitively, but the the Italian importer does not seem to have any available and therefore blindly purchases or looks; unpleasant situation that makes you want to buy on the net in another state, where you can find even cheaper prices. For the moment I wait for my trusted dealer to tell me something specific then I will decide what to do.

For the moment I tried to swap the eyepieces between the two telescopes and I found that the 20-40x on the 66 is good over the entire focal range and the 20-60x on the 613 does not have AC over almost the entire focal range, possible that the telescope is more correct? Also I'm thinking of getting a 30xW will I have more cleanliness and detail than the new zoom? I know there are several models which are good?

A greeting and thanks to the whole forum.
Luca
 

KC Foggin

Super Moderator
Staff member
Opus Editor
Supporter
United States
Hi there and a warm welcome to you from those of us on staff here at BirdForum (y)

We're glad you found us and thanks for taking a moment to say hello. Please join in wherever you like ;)
 

Kits

Picture Picker
Welcome to Birdforum! I am sure that you will find lots to interest you here and I hope you enjoy your visits.
 

delia todd

If I said the wrong thing it was a Senior Moment
Staff member
Opus Editor
Supporter
Scotland
Hi Luca and a warm welcome from me too.

I'll move your post to the Kowa Telescope forum, where you should get the expert advice you need.

I'm sure you will enjoy it here and I hope to hear about all the birds you see when out and about.
 

jring

Well-known member
Hi,

first of all, welcome to birdforum!

A good example of TSN-3 should offer a crisp image at 60x too - with a proper EP and in good seeing. The old Kowa 20-60x zoom with the rubber eyecup is usually not great.

Regarding chromatic aberration or CA, there are two kinds - one is called axial or longitudinal CA and is not what most people would call CA - it just leads to a degraded image at higher magnification. Its amount is determined by the objective construction and/or manufacturing tolerances.

The other kind is called transversal or lateral CA and are the typical yellow and purple fringes at high contrast edges. This is usually mainly determined by the eyepiece construction and most of the time it's mainly visible off axis while the center is ok.

I'm not quite sure about your results - so you were comparing your 77mm TSN-3 with the old 20-60x zoom to a 613 with a 20-40x zoom (which is a rather rare beast). At some point you were writing about a 66 - that should read 77 as your TSN-3? Or did you have a third instrument in the comparison?

In general, all the Kowa small body scopes (except for the 82SV) do have the same focal length of 420mm. Since their apertures vary quite a bit from 60 to 77mm, so do their focal ratios from pretty relaxed f7 for the 60mm versions to a rather fast f5.5 for 77mm. The latter calls for better glass (or rather fluorite crystal in case of your TSN-3) while the smaller aperture models work fine with ED (extra low dispersion) glass.

A faster focal ratio also does not work well with all eyepieces and might lead to off axis CA and other aberrations at higher magnifications.

Maybe you could try a star test at 60x and describe what you see... ideally equal patterns of concentric circles a bit off best focus...

Joachim
 

Luca1970

Member
Italy
Hi Joachim, yes I wrote 66, but I meant 60, yes 20-60 is just the one with the rubber shell.

What I see is a clear halo (white blue) around gray subjects (specifically, very visible around gray herons) when they are in areas of high contrast even if the subject is in the center of the image. It already happens a little before 40x on the TSN3, the thing I find strange is that with the 613 it is barely visible around 60x.

If, on the other hand, I use the 20-40x that was supplied with the 613 even at 40x there is no trace of the outline, thinking about it, I imagine that the problem is in the treatment of the anti-reflective eyepiece that with the single-layer treatment of TSN3 creates the halo. I imagine that the anti-reflective treatment of the 613 and the 20-40x have improved and therefore show less of the problem. I'm confident the TSE-Z9B doesn't have this problem.

Thanks for the valuable advice.
Luca
 

jring

Well-known member
Hi Luca,

yes, as I wrote, the old 20-60 zoom from the 90s is not great... and usually lateral CA is caused mainly by the EP, but of course the focal ratio does play a role - and the TSN-3 is quite a bit faster than the 613... and the steeper light cone makes things more difficult for the EP.

Did you try the TSN-3 with the 20-40 zoom and did you see the same CA below or at 40x there?

I have a cherry TSN-3 body (w/o protective glass) with an SDLv2 zoom from Opticron, which works really great up to 54x (unfortunately probably not an option on your newer model with protective glass).

My 613 is usually used with the 30 wide and sometimes with the 1.6x extender... Also nice but I usually grab the TSN-3..

PS: I have a spare TSE-Z9B which I got through a package deal (together with the 613 iirc) and which I might be willing to part with... and would even take back if it doesn't work for you... if you're interested, send me a PM...

Joachim
 

Luca1970

Member
Italy
Hi Joachim,

I hadn't thought about the focal ratio: optical physics was not my forte when I went to school!

Yes, I tried the 20-40x on the TSN3, it still has a very small fringe, but definitely much less than the 20-60 at 40x.

I have read your cherry TSN3, and of the operation with the SDLv2 and I must say that if I have decided to take the TSN3 in my possession it is precisely for this reason I have read in your interventions here. I already knew that mine would not be compatible with Opticron eyepieces, but it was too good and too cheap to miss, also I was hoping that Kowa Italia had some eyepieces to try before buying, but unfortunately it is not.

These days I send you a PM: I think yours is an offer not to be missed.

Luca
 

z-ben

Well-known member
England
I have a tsn 3 and have no problem fitting an opticron eyepiece there is about 1mm of clearance without the o ring even though it has the protective glass window inside it is better with the opticron HDF 4O8062 than the kowa 30w or the 20w and I did do these comparisons in poor light .
 

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