Across
- 2. The angular distance the Moon or a planet is from the Sun
- 3. The diameter of a telescope’s main lens or mirror — and the scope’s most important attribute. As a rule of thumb, a telescope’s maximum useful magnification is 50 times its aperture in inches
- 4. The celestial equivalent of latitude, denoting how far (in degrees) an object in the sky lies north or south of the celestial equator.
- 7. When the Moon or a planet appears especially close either to another planet or to a bright star.
- 8. Sunlight reflected by Earth that makes the otherwise dark part of the Moon glow faintly. It’s especially obvious during the Moon’s thin crescent phases.
- 10. An event that occurs when the shadow of a planet or moon falls upon a second body. A solar eclipse occurs when the Moon’s shadow falls upon Earth, which we see as the Moon blocking the Sun.
- 12. A type of Newtonian reflector, made popular by amateur astronomer John Dobson, that uses a simple but highly effective wooden mount.
- 15. Any prominent star pattern that isn’t a whole constellation, such as the Northern Cross or the Big Dipper.
- 16. A distinctive pattern of stars used informally to organize a part of the sky.
- 17. A lens that’s placed into the focusing tube to effectively double or triple a telescope’s focal length and, in turn, the magnification of any eyepiece used with it.
- 20. A grid system for locating things in the sky. It’s anchored to the celestial poles (directly above Earth’s north and south poles) and the celestial equator (directly above Earth’s equator). Declination and right ascension are the celestial equivalents of latitude and longitude.
- 21. A concentration of mass so dense that nothing — not even light — can escape its gravitational pull once swallowed up.
- 22. The measure of how much an orbit deviates from being circular.
- 23. The eyes’ transition to night vision, in order to see faint objects.
Down
- 1. Denotes an object near a celestial pole that never dips below the horizon as Earth rotates and thus does not rise or set.
- 5. A telescope with a mirror in the back and a lens in the front.
- 6. A solid body orbiting the Sun that consists of metal and rock. Most are only a few miles in diameter and are found between the orbits of Mars and Jupiter, too small and far away to be seen easily in a small telescope. A few venture closer to the Sun and cross Earth’s orbit.
- 9. The moment when a celestial object crosses the meridian and is thus at its highest above the horizon.
- 11. The average distance from Earth to the Sun, slightly less than 93 million miles
- 13. Traditionally, something that happens rarely or never. More recently, this has come to mean the second full Moon in a single calendar month.
- 14. A “dirty snowball” of ice and rocky debris, typically a few miles across, that orbits the Sun in a long ellipse. When close to the Sun, the warmth evaporates the ice in the nucleus to form a coma (cloud of gas) and a tail.
- 16. Aligning the optical elements of a telescope so that they all point in the proper direction.
- 18. Viewing an object by looking slightly to its side. This technique can help you detect faint objects that are invisible when you stare directly at them.
- 19. Two stars that lie very close to, and are often orbiting, each other