Kestrel 4500 Pocket Weather Tracker with digital compass and night vision preserving backlight.
Measurements: Heading (true and magnetic), Wind Direction, Crosswind, Headwind/Tailwind, Altitude, Pressure Trend, Barometric Pressure, Relative Humidity, Heat Stress Index, Dewpoint, Wet Bulb Temperature, Density Altitude, Wind Chill, Air, Snow and Water Temperatures, Current and Average Wind Speeds and Maximum Wind Gust, Customizable 2900 Data Point Storage, Data Upload (with optional interface)
Note: This unit has a night-vision preserving backlight which helps users to sustain natural night vision. The NV's backlight incorporates an optical filter to reduce overall brightness and minimize blue and green spectrum light to preserve night vision. Additionally, NV backlights are also much dimmer than a standard backlight, making it more difficult to detect with the naked eye in night operations. This backlight appears soft greyish pink, not red, and is still in the visible spectrum, so is not compatible with night-vision equipment.
It takes 30 to 45 minutes for the average eye to adapt to darkness and maximize night vision. Even a short burst of white, yellow, green or blue light “bleaches out” the rod cell photoreceptors in the eye and causes night blindness until the entire adaptation process can take place again. Light in the red spectrum does not cause this “bleaching out”, preventing night blindness and night vision fatigue.