Review of the Kowa TSN-55A Spotting Scope

Have you rated your binoculars yet?

7 May 2026

Arkadiusz Olech

1. Introduction

Even several years ago the TSN-550 Prominar was the flagship series of Kowa's small spotting scopes. In the angled version it weighed 810 grams and was 271 mm long, offering you an eyepiece with the magnification range from 15 do 45 times and an eye relief distance of 16-16.5 mm. This type of construction, with a 3x optical zoom, was quite common among many optics producers.

The eyepiece, along with the focusing module, allowed you to set the focus from 3 meters and offered fields of view ranging from 37.5 to 58.5 degrees. For a top-of-the-range product of a renowned producer these values were rather low. Especially the field of view at the smallest magnification was so narrow that you got an effect of looking through a keyhole.

Review of the Kowa TSN-55A Spotting Scope - Introduction

In 2024 Kowa decided to change that and they launched a new series marked as TSN-55 Prominar, offered in two variants, straight and angled.

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Introducing a new, much bigger eyepiece was the most important change. Its magnification range decreased to a span from 17-40 times. It is noticeably less useful range meaning that you get just 2.35x zoom, not 3x like in case of the predecessor.

Still, what we got instead? Firstly, the eye relief distance increased and now it amounts to 17 mm, no matter what magnification you employ. Secondly, the value of the minimum focusing distance decreased to 2.8 meters. Thirdly, and most importantly, the range of fields of view increased significantly.

The spotting scope provides us angles of view from 3.64 to 2.0 deg and they mean the apparent field of the eyepiece changes from 61.9 to 80 deg (calculation done using simple formula). These are outstanding values that provide you a great comfort of observations.

Using such an eyepiece had to increase its weight and the weight of the whole spotting scope. The angled version of the TSN-55A weighs now 965 grams, by 155 grams more than its predecessor, that's over 19% more in percentage terms. The shape and layout of the main barrel was changed as well so the whole set, with the eyepiece, measures now just 255 mm compared to 271 mm of its predecessor.

Overall it seems that limiting magnifications to the 17-40 x range was a price worth paying because you got a lot instead.