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Astronomy & Telescopes Glossary - N
Nadir - The point directly below an observer.
NEA - Abbreviation for Near-Earth Asteroid. Asteroids whose orbits bring them within 1.3 AU of the Sun. Also called Earth-Approaching asteroids. NEAs probably came from the main asteroid belt.
Neap tides - Neap tides occur when the gravitational forces of the Moon and the Sun are perpendicular to one another and occur during quarter moons.
NEAT - Abbreviation for Near-Earth Asteroid Tracking, which is a joint NASAJPL program that tracks near-earth asteroids (NEAs).
Nebula - A large, deep-space object comprised of gas and dust. A nebula that glows with its own light is called an emission nebula while one lit from nearby stars is called a reflection nebula. A nebula that blocks light is called a dark nebula.
NEO - Abbreviation for Near-Earth Object, which is any comet or asteroid that is close to the Earth's orbit.
New General Catalog - A classification system that lists over 13,000 deep-sky celestial objects. Abbreviated as NGC.
Newtonian telescope - A reflector telescope that uses a a mirror set in the lower end of a tube. A small, secondary mirror near the upper end of the tube reflects the beam to the eyepiece.
Northern lights - Another name for auroras that appear in the Northern Hemisphere.
North Star - The star, also called the Pole star, located almost due north used for navigation and telescope alignment. Polaris is currently the pole star of the Northern Hemisphere.