Kowa TSN-771 telescope

‘Re-engineered, not revamped.’ That’s the message that comes across with the new TSN-770 series from Kowa, a renowned manufacturer with a secure niche in the optics market. The new design incorporates an advanced lens system, which enables the telescope’s body to be built compactly, and takes on board the growing trend to incorporate dual focusing. There is also a new range of superior eyepieces and an equally new locking and quick-release mechanism to respectively secure and change them.

The TSN-771 represents the angled version of the two ‘basic’ models in the series. A premium is payable for the equivalent high specification model, the TSN-773, which features Kowa’s fluorite crystal lenses and is designed to deliver a superior image, particularly in poor light conditions. The TSN-771 is, however, a formidable piece of equipment. Weighing 1,655 g with the zoom eyepiece included, at first glance this magnesium alloy telescope appears heavy, but this deception results from the weight being condensed into a compact and solid body. The use of rubber armour is restricted to the lens hood, while the only other rubber to be found surrounds the rigid eye-cups, which extend outward to three click-stops beyond the base setting on both the zoom and the fixed magnification eyepieces.

The eyepieces themselves are waterproof and nitrogen purged to prevent fogging, and they can be very easily attached to, and removed from, the scope body. An internal automatic locking device ensures they are secure after they have been inserted, and their subsequent removal is facilitated by the depression of a quick-release button recessed into the base of the scope’s eyepiece port. This stylish, though simple, piece of engineering contributes significantly to the ease of use of this scope, as does the new fast-focusing system, which also features in the larger 880 series.

Kowa has been quick to point out that its focusing mechanism is not simply a system that allows further ‘fine tuning’ of an image already in focus. Instead it represents a means of switching very rapidly between close and distant focusing, thus dispensing with the need for multiple turns of a single knob – and the time that takes.

I found this mechanism very useful in the field; fewer than two complete turns of the larger fast-focusing wheel allowed me to adjust the focus quickly from relatively close birds viewed from a hide to a gull or raptor flying in the distance. The wheels are mounted concentrically at the centre top of the scope’s body, which allows for both left-handed and right-handed use. Both wheels turn freely and lend themselves for use with the index finger for fast focusing and the middle finger for general focus.

Another mechanical feature – perhaps of less importance – is the rotating tripod foot attachment, which can be click-locked in six different positions around the body.

The image delivered by the TSN-771 is, unsurprisingly, very good indeed. I field-tested the scope using the 30x magnification wide angle eyepiece and the 20-60x zoom and both performed admirably, returning clean, sharp-to-the- edge images with good contrast, true-to-life colour tones and a very low level of colour fringing. Most of the latter was restricted to the periphery of the field of view and was more detectable at higher magnifications with the zoom eyepiece. Image brightness was significantly greater with the fixed-magnification eyepiece installed, but the zoom was not far behind, especially at lower magnifications. The difference between the two eyepieces was more evident at low light intensities.

As much as I liked the zoom, I must confess I favoured the 30x wide-angle eyepiece as a good all-rounder when used with this Kowa non-fluorite glass model. Its brightness and wide field of view – almost 42 m at 1,000 m – are excellent for general viewing.

Accessories for this scope include a stay-on case made of a synthetic material, which is shower proof, padded and ribbed. Leatherette pouches for the safekeeping of eyepieces are available, as are adaptors that allow existing eyepieces from the 600, 660 and 820 series to fit the new scopes in the 770 and 880 series.

Whether the relatively high price for this basic model is justified is a matter of debate but, as with most optics, you can buy the TSN-770 for less than the recommended retail price if you shop around.

First published in Birdwatch 180: 45(June 2007)