Kowa TSN-99a vs. Leica APO 82 Televid (1 Viewer)

[jcwu88]

Hi Jay,

I would love to believe that (as then my so far slightly undercorrected - that's what clear rings before and mushy later means) TSN-3 might be actually better than it looks in star test - and yes, the daytime view is very sharp even at high magnification.

Although regarding that link I have to say that it is a far stretch to say that the 2nd star test with green filter results into sth. as bad as the 3rd one in white light... the effect is much less pronounced.
Also stating that "the best test of any optics is in focus" leaves me kinda puzzled... for the in focus image to be visibly degraded you need quite strong aberrations - often worse than diffraction limited. The normal star test with out of focus diffraction patterns is much more sensitive than that.
Lastly it does not really look like a carefully researched article when the "noted optical designer of the Astro Physics refractors" is called Roland Christensen... the man's surname is Christen.

See the link below for what the effect looks like in a good scope (white light in post 1, green light in post 20):

Doubts about Taka FC100D star test - Refractors - Cloudy Nights

Page 1 of 4 - Doubts about Taka FC100D star test - posted in Refractors : Good morning everyone, attached you will find star test of my new Takahashi FC100DF (100 mm f/7,4 fluorite doublet), in white light. I know that apochromats often dont show identical extrafocal and intrafocal patterns...

www.cloudynights.com

The Tak in that link has an admittedly easier task being quite a bit smaller at 100 vs 140mm aperture plus slightly slower at f7.4 vs f7 and also being a fluorite doublet vs a doublet with an unnamed ED glass - might be fpl-51 or so which will be a stretch to get to work acceptable in a doublet that large, fpl-53 et al. performance should be close to fluorite though at same aperture and focal ratio.

Joachim

Hi Joachim,

Thank you for links of the Tak star test. That’s almost a perfect scope/test and the OP had quite a lot analytical data on it and gears there.

Yes. The link I posted has some quirks and misspelled Roland Christen. I also suspected the part to check on focus image. But the referred (thought misspelled name ) comments of apochromatic test from Roland was also mentioned on from the Tak test thread discussion.

I don’t have astro scopes and instruments like green filters and 532nm lasers to check those fine test so I can’t comment.

I have simple star test with artificial star as described this forum with my spotting scopes. Thought I can’t take pictures but for seeing the same trends of patterns (clear inner rings and barely visible outside rings). That puzzled me since those scopes are Nikon ED fieldscope and Kowa fluorite. Statistically if they’re all bad samples based on star test results with excess SA, the chance is so unfortunately high? (5/5)
For curiosity to find the explanation so Googled the link with Roland’s comments. For me it is not perfect but explained some of my observations.

Jay

 

[jcwu88]

Hi Joachim,

Thank you for links of the Tak star test. That’s almost a perfect scope/test and the OP had quite a lot analytical data on it and gears there.

Yes. The link I posted has some quirks and misspelled Roland Christen. I also suspected the part to check on focus image. But the referred (thought misspelled name ) comments of apochromatic test from Roland was also mentioned on from the Tak test thread discussion.

I don’t have astro scopes and instruments like green filters and 532nm lasers to check those fine test so I can’t comment.

I have simple star test with artificial star as described this forum with my spotting scopes. Thought I can’t take pictures but for seeing the same trends of patterns (clear inner rings and barely visible outside rings). That puzzled me since those scopes are Nikon ED fieldscope and Kowa fluorite. Statistically if they’re all bad samples based on star test results with excess SA, the chance is so unfortunately high? (5/5)
For curiosity to find the explanation so Googled the link with Roland’s comments. For me it is not perfect but explained some of my observations.

Jay

Here are the original comments from Roland Christen:

Notes on Star Testing Refractors

Star Testing Complex Optical Systems

 

[lassa8]

Regarding the original question about size being a drawback, I was actually surprised by the size/weight of the 99a. I guess I was expecting it to be a behemoth, but I've really had no issues transporting it around as a ~40 year old relatively fit individual. For long hikes I just toss it and a tripod in my backpack and off I go.

 

[biowizard]

I've just come home from a three-week vacation in St Lucia, West Indies. Staying on a tropical island, in several different hotels, two of which had amazing sea views (including across the 21-mile "channel" to neighbouring Martinique), and the same two plus another of which also had plenty of lush, tropical foliage (and associated wildlife) closer to hand, I decided this time to leave my beloved Swarovski EL 10x50 binos behind, and instead travel with my 40-or-so year old Kowa TSN-3 Prominar scope, with the original 30x WIDE eyepiece.

Despite its age, my TSN-3 is still in mint condition, with 100% clean and clear optics. I had forgotten JUST how brilliantly sharp its image is, totally clear of any colour fringing largely thanks to its 100% Fluorite objective lens. Whether at close range, counting the scales on a small lizard's head, or watching insects go about their business, or at a distance, seeing individual cars driving on that next island, 21 miles across the ocean, the image quality of my KOWA still blows my mind away.

During the COVID pandemic, I considered replacing the TSN-3 with a more modern scope, perhaps one of the Swaro ATX or STX series module/eyepiece combinations, mainly because the thought "newer means better" kept crossing my mind. And then I'd take out my TSN-3 in the back garden, and remind myself how basically perfect it is, so why replace it!

When I bought the KOWA in about 1986, I compared it with the best Zeiss, Leica and Nikon scopes that my dealer had, and also with the non-fluorite KOWA TSN-1. None of the latter got anywhere near close to the truly amazing image of the TSN-3. It was frankly a no-brainer which scope to get, and I paired it with a third-party stay-on case and a massively solid Manfrotto tripod with a video-pan head.

No regrets whatsoever, and thus far, still no real intention of changing to a newer model!