Focus sensitivity on Kowa 663 (1 Viewer)

Might be a bit of a strange question, but....

Anyone who has / uses a Kowa TSN663 prominar - can you advise on the number of rotations of the focus wheel to go from close focus to infinity? Also whether there are any issues with obtaining sharp focus on the scope?

The reason I ask is because I am looking for a new scope. I currently use a Nikon ED82, fantastic image, bright and clear, but the hypersensitive focus is just not for me. I have battled with it for a few years now and have accepted that I will never get used to it, I do not like helical focus, certainly not very sensitive ones like on the Nikon.
I am therefore looking to go back to a focus wheel scope (my previous scopes were Leica Televid 77 and Kowa TSN1) but I do not want to fall into the same trap of buying a scope only to find it has very sensitive / critical focus. I cannot find any info online about the focus with the exception of a Birdwatch review back in 2011 where it specifically mentioned the sensitivity of the focus wheel.
Another problem is that there is nowhere around here that I can actually look through one, the nearest place is probably 200 miles away so I will need to take a bit of a 'leap of faith' with this. Ideally I would get a scope with dual focus but I have considered the alternatives in this price range (Zeiss 65, Vortex Razor - old type) and decided against them. As I am not Rockefeller my budget does not stretch to a 773 / 883.
So...anyone has any opinions on this that may assist?
Appreciate any input.
Thanks

Hi,

anecdotal evidence only since I don't own a 663 scope and only get to use one once in a while from a fellow birder. I don't remember the focus from being any different than my TSN-3 and also the view was comparable.

The fact that the 663 has ED glass instead of CaF2 is offset by the slightly slower focal ratio of f6.4 vs. f5.5 in the TSN-3.

Maybe one of the 663 owners can chime in...

Joachim

jring said:

Hi,

anecdotal evidence only since I don't own a 663 scope and only get to use one once in a while from a fellow birder. I don't remember the focus from being any different than my TSN-3 and also the view was comparable.

The fact that the 663 has ED glass instead of CaF2 is offset by the slightly slower focal ratio of f6.4 vs. f5.5 in the TSN-3.

Maybe one of the 663 owners can chime in...

Joachim

Click to expand...

Thanks Joachim

Any owners of the 663 got any advice?

Hello, I own a Kowa TSN 663m, I did not understand what you need to know?, The speed of focus? Giorgio

Piskeddu said:

Hello, I own a Kowa TSN 663m, I did not understand what you need to know?, The speed of focus? Giorgio

Click to expand...

Hello Giorgio

I am interested in knowing the focus characteristics of the scope and how easy it is to achieve a sharp focus. My question regarding the number of rotations of the wheel from close focus to infinity is to try and grasp whether the focus is overly sensitive (like what I have now). I may be wrong but I would assume that a scope that has a higher number of rotations would be easier to focus sharply whereas one with only a short number may be a struggle. I know that the 883 is stated as only two turns from close focus to infinity but that scope has the benefit of the dual (fine) focus.
Hope you understand what I am getting at.
Chris

Any Kowa TSN663 owners and users out there who can help?

Have I frightened people off?

Any info is helpful as I am looking to potentially purchase soon before the current sale expires...

Thanks

hello, I see tonight at home to do a test and then refer the result, surely have dual focus wheel to focus on the end makes the difference.

Hi,

in my expericence a dual focus wheel is rarely the deciding factor whether I can reach good focus or not, at least not visually. I don't even have one on my spotting scope but my ED80 astro refractor has one.

The question is rather if there is a well defined focus point visible in the instrument at a given magnification. This is determined by the longitudinal chromatic aberration (this is a property of the instrument design and glasses used) and the depth of field (this depends on focal ratio - lower/faster focal ratios have a shallower depth of field).

The longitudinal CA leads to slightly different focus points for light of different colors. As long as the focus points for all colors fall inside the depth of field, you have a well defined focus point - the image snaps into focus. If that is not the case, the image remains slightly mushy even at best focus - dual focus will not stop you from hunting focus then.
This is the reason why your usual non-ED spotter is not going to work well over 40x or so.

Another question is whether you can adjust focus w/o disturbing the image too much at high magnification - I can do this better with just one finger with a top mounted focuser if it is reasonably smooth than with the whole hand for those rings around the body. But that's probably a matter of taste and practice.

If you are trying to reach focus with a camera at prime focus, things might be a bit different but even then, having focusing aids like a bahtinov mask at night or focus peaking/loupe during dailight is more important.

Joachim

I've been following this thread and wondering whether the OP's focus "sensitivity" might be caused by optical problems rather than problems with the mechanical focuser. Joachim's post brings up one of the aberrations that can lead to difficulty reaching a secure focus. In my experience there are a few others that tend to be highly variable from unit to unit, like spherical aberration, astigmatism, pinching and coma. All of these are well controlled in a good example of the Nikon 82ED, but as with every scope, an excessive amount of one or more in a particular specimen could make achieving really good focus difficult.

I tested a Kowa 663 a few years ago. That particular unit had too much astigmatism and spherical aberration to reach a truly sharp focus. I'm sure there are better examples, but the quality of a particular unit is never guaranteed. Certainly, if equally good units of the Nikon 82ED and the Kowa 663 were compared for image quality the Nikon would win easily just from larger aperture alone, but in the real world of sample variation a lemon Nikon 82ED could be more difficult to bring to a sharp focus than a cherry Kowa 663.

Henry

The focus is precise, the minimum focusing distance to infinity spend more turns of the wheel, the CA is very limited, I appear only once on snowy mountain crete but only booby top of the view, for interderci at 12 clock, dall'ottanta% field of view, I hope you have been helpful. Giorgio

henry link said:

I've been following this thread and wondering whether the OP's focus "sensitivity" might be caused by optical problems rather than problems with the mechanical focuser...

Click to expand...

From the original post, I suspect not. I find the focus ratio of the 82ED excellent for quick yet precise focus at 30x, but dialing in sharp focus at 75x without over or undershooting the best setting can be difficult. I find it helpful to put my fingers at the edge of the collar, so my fingers drag over the body of the scope while turning the focuser. Doing so damps small irregularities in my muscle movements. It also allows me to stop turning at precise points by squeezing my fingers harder against the scope body rather than through precise movements of the large arm and forearm muscles that are usually employed in turning the focus collar.

--AP

Thanks for the comments everyone. I have taken the plunge and ordered a Kowa TSN-663 with the zoom, I will be able to take it out this weekend and give it a good test, at the end of the day that is the only way I will be able to tell if it works for me.

If it doesn't then it'll cost me a fiver to send back within 14 days.

If it does work for me then I'll be looking to sell the ED82A with the 38xW eyepiece.

Thanks

Thanks to everyone for the comments on here.

Just to follow up, I did purchase the 663 (which actually turned out to be 663M, even though it was only advertised as 663 - bonus!) and I am very happy with it. The FOV is narrower than what I have been used to with a Nikon ED82 and a 38xW eyepiece, but I don't feel like I am missing out much.

The image is very bright and clear, contrast is amazing. In the interests of a fair review, I don't think it is sharp all the way to the edge of the image, maybe the outer 5% is not completely sharp. Also the image brightness drops off on the zoom at 60x a bit more than I expected. However I have tested it in a number of different conditions (bright sunshine, late evening gloom) and it is only when the light really goes that the zoom on high mag struggles a bit. At magnifications from 20 - 40ish it is a pleasure to use. The big difference is the focus.....it is MUCH easier to get a sharp image than with the ED82. I pondered beforehand as to whether dual focus would be needed but the single focus wheel on the 663 is fine.

This is probably the biggest thing to warn of: focus systems. I assumed (incorrectly) that I would have no problems using a helical focus - but after using a TSN1 and then Leica APO Televid for the previous 15 - 20 years prior to getting the ED82, I had become used to a certain focus system. The big problem that I had, and one that I'm sure that many people will have, is finding a shop that has the scope that you are interested in (within 200 miles) and so a lot of purchasing will be done without trying. I have had to do the same thing again with the 663 as there were no shops anywhere within sniffing distance, but if it had not worked out I would have sent it straight back. This was the biggest issue I had with the ED82, I never really fell 'in love' with it because of the focus and I actually started to despise it as it was impacting on my birding. There is nothing 'wrong' with the scope, optically it is stunning, but the focus system in just not for me and that can make a massive difference. But for others the helical focus is everything they want and they don't like playing with their knobs (I have greatly enjoyed playing with knobs for over two decades, I strongly recommend it).

I am happy with my 663M and looking forward to using it more in the field

Hi Chris. The 663 is certainly a lovely scope and I hope you enjoy yours. If you can at some point I'd definitely recommend getting hold of the twist-up 20x or 30x fixed eyepiece too, as I love the view through those (I'd say I use the 30x most of the time on mine) and it would offer a good alternative to the zoom and give you more FOV.

Grando said:

Hi Chris. The 663 is certainly a lovely scope and I hope you enjoy yours. If you can at some point I'd definitely recommend getting hold of the twist-up 20x or 30x fixed eyepiece too, as I love the view through those (I'd say I use the 30x most of the time on mine) and it would offer a good alternative to the zoom and give you more FOV.

Click to expand...

Yes, I've certainly got the 30x on my future wish list, especially for seawatching. I just need to let my credit card recover from the near fatal injury that has been dealt through the scope purchase.

But money isn't everything and the smile that this scope produces on my face every time I use it makes the cost worthwhile.

Grando said:

Hi Chris. The 663 is certainly a lovely scope and I hope you enjoy yours. If you can at some point I'd definitely recommend getting hold of the twist-up 20x or 30x fixed eyepiece too, as I love the view through those (I'd say I use the 30x most of the time on mine) and it would offer a good alternative to the zoom and give you more FOV.

Click to expand...

Agreed. 30x is a great eyepiece.