The Kowa PROMINAR TSN-773 uses an XD objective lens with low dispersion properties to diminish chromatic aberration. The performance and compactness of these spotting scopes are second to no other scopes in this class. The housing is waterproof to JIS protection class 7 and filled with dry nitrogen gas to prevent the lens from fogging. JIS 7 = Japanese Industrial Standard / class 7 = Protected against the effects of temporary immersion in water.
Dual focus mechanism (Quick and fine focusing)
The well established Kowa focus system has progressed to a new dual focus system. The quick focus, with a large and easy to turn knob, will focus from infinity to five meters in two revolutions. The fine focus, with smooth movements and pinpoint accuracy, is extremely useful at high magnifications and for digiscoping systems. Eyepiece locking mechanism Kowa's standard eyepiece bayonet mount has been passed down to these new spotting scopes with a new attractive feature. An eyepiece locking mechanism has been added to the mount to prevent the eyepiece from getting lost or falling out unexpectedly.
Magnesium alloy body
The magnesium alloy body made by a sophisticated molding process called thixotrophic molding has the feel and strength of a traditional metal body with decreased weight when compared to other large-diameter scopes. The rugged structure can tolerate the severest conditions and provides confidence and a sense of security for the user.
One of the major causes of deterioration of viewing quality in optics is chromatic aberration (color blur). Chromatic aberration occurs due to the dispersion of light and the different wavelengths of light focusing on different positions, resulting in a red or purple fringing around the image. The optimum optical material to minimize chromatic aberration is fluorite crystal. This technology is the result of many years of optical design and has realized great reduction in chromatic aberration, while maintaining a large diameter lens and high contrast images when compared with conventional models. The XD lens used in our TSN-773/774 PROMINAR models has characteristics similar to those of fluorite crystal to significantly reduce the chromatic aberration. All lenses are environmentally friendly Eco-Glass. (Eco-Glass is an environmentally friendly glass that does not contain lead or other harmful substances.)
When an XD lens (eXtra-low-Dispersion-lens) is paired with a concave lens with special dispersion properties, chromatic aberration is almost eliminated. The performance of spotting scopes with XD lenses is very close to that of our flagship models with fluorite crystal.
The telephoto lens design of using 5 lens elements in 4 groups has successfully shortened the overall length of the scope while keeping a large diameter objective lens without sacrificing optical performance. The adoption of an inner focusing system has made the prism box light and compact and at the same time decreases the amount of image movement when compared to conventional prism focusing systems. The highly achromatized objective lens makes the scope as compact as a 60mm class scope without sacrificing performance.
Objective Lens Diameter: 77mm
Minimum Focus Distance: 5m
Diameter of Filter: 82mm
25-60x Zoom Eyepiece (TE-11WZ):
This high-performance zoom eyepiece contains 2 XD-lenses, a first for any Kowa eyepiece. The field of view is increased by around 20% over the original 20-60x zoom eyepiece. Images are delivered with outstanding sharpness even at 60x magnification and chromatic aberration is limited at the highest level while eye relief remains constant throughout the magnification range.
Field of view: (at 1,000m range) 42m - 23m
Exit Pupil: 3.5mm - 1.5mm
Eye Relief: 17mm