Astronomy & telescopes glossary - N

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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.

Guide to Amateur Astronomy, Planets and Constellations

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