Across
- 1. the measure of how much an orbit deviates from being circular
- 3. the celestial equivalent of latitude, denoting how far (in degrees) an object in the sky lies north or south of the celestial equator
- 7. a telescope's main light-gathering lens or mirror
- 8. any prominent star pattern that isn’t a whole constellation, such as the Northern Cross or the Big Dipper
- 10. the edge of a celestial object's visable disk
- 11. a temporary dark blemish on the surface of the Sun that is a planet-size region of gas cooler than its surroundings
- 12. traditionally, something that happens rarely or never. more recently, this has come to mean the second full Moon in a single calendar month
Down
- 2. when the Moon or a planet appears especially close either to another planet or to a bright star
- 4. the fraction of the moon or other body that we see illuminated by sunlight
- 5. a lens or mirror’s focal length divided by its aperture
- 6. the point in the sky that is directly overhead
- 9. an increase in meteor activity at certain times of the year due to Earth passing through a stream of particles along a comet’s orbit around the sun