Full-field Beam Converger with quartz hardcoat replaces conventional half-silvered mirror. Horizon and astrobody images are combined in a single full-field for easy, reliable sights under the most difficult conditions. -Special mineral coating is selective for different wavelengths of light. Horizon is transmitted in one color region and the star or sun in another. -Improved reinforced plastic stiffens frame for greater measurement accuracy. -High-efficiency LED (solid-state Light Emitting Diode) illumination system, which floods arc and drum with soft light. The LED will last for the lifetime* of the sextant. Batteries, which are included, will last up to 10 times longer than with regular bulbs. This is another Davis first! Positive "push-on" switching action, with vinyl boot water protection. *Based on manufacturer`s data, average LED `half-life` is approximately 10 years if operated continuously.