Review of the WAT-120N Video Camera
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Watec 120N A very attractive instrument for stargazing is the WAT-120N video camera manufactured by Watec Co., Ltd., Japan. It's maximum exposure time is 1/30th second, however, by accumulating up to 256 frames 1/30th second each before outputting an image, the camera is actually capable of 8.5 seconds exposure time. Not only does this result in high sensitivity but also in reduced noise compared with single frame exposures since images are 'added' in memory.

The camera provides a monochrome composite-video signal which can be routed to almost any TV monitor with a standard 'yellow video input'. The signal may as well be fed to a computer with composite video input, most commonly provided by a "video grabber card".
2500mm f20
Equipped with a C mount adapter, conventional exchangeable lenses can be attached for wide or zoomed field observations. Exposure times of several seconds with zoom lenses will demand a mount with tracking capabilities, otherwise stars will appear as trails. Short focal length CCTV lenses will provide a wide field for meteor observations without requiring tracking.

Since optical glass quality is a less important factor, used or junk lenses will provide most satisfactory results. In spite of the high camera sensitivity, fast lenses, say not slower than F/4 are the best choice. Of course, the WAT-120N can also be plugged into the eyepiece sleeve of an accurately guided telescope using a C mount sleeve adaptor (such as the Tomy/Borg part number 7511) for focal point observation.

Plug the camera with a lens, say, 135mm on a remote controlled telescope and connect the video to a large LCD monitor to allow a greater audience to watch the real-time sky, including meteors, satellites and airplaines indoors.

The WAT-120N packs top-notch imaging electronics in a compact solid body weighing 150 grams and comes with an intuitively designed, handy remote control. It requires a single rail +12VDC supply (actually from +9.5 to +15V) provided by a mains adapter, car cigarette lighter, or most conveniently stripped off from the telescope power supply which is possible thanks to the low current consumption of mere 160mA at maximum. A detailed specification sheet in English can be downloaded from the manufacturer's web site at

A camera containing exactly the same electronics is known in the US as StellaCam II. Sky & Telescope have published a more detailed review in their October 2004 issue starting on page 86. The review whitnesses what the camera can really perform under dark skies.

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