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Across 2. telescope that uses a set of lenses to gather and focus light 6. imaginary point in the sky directly above the observer on earth 7. instrument that collects electromagnetic radiation from the sky and conc it for better observation 8. the longest constellation 10. stated that the earth was the center of the universe, and the planets revolve around the sun adn they all revolve around the earth 16. the time required for the Earth to rotate once on it's axis 18. telescope uses curved mirrors to gather and focus light 20. the number of constellations 21. the time required for the Earth to orbit the sun once 24. a year in which an extra day is added to the calendar 25. a section of the sky that contains a recognizable star pattern 26. unit of length equal to the dist light travels through space in 1 year 27. explained why planets orbit the sun and why moons orbit planets 28. the line where the sky and the earth appear to meet

Down 1. the angle between an object in the sky and the horizon 3. study of all physical objects beyond earth 4. all the wavelengths of electromagnetic radiation 5. roughly the amount of time required for the moon to orbit the Earth once 9. a measure of how far east an object is from the point at which the sun appears on the first day of spring 11. first person to use a telescope to observe celestial bodies 12. stated that the earth was the center of the universe 13. imaginary circle created by extending earth's equator into space 14. apparent path the sun takes across the celestial sphere each year 15. the biggest constellation by volume 17. stated that the sun was the center of the universe 19. a measure of how far north or south an object is from the celestial equator 22. student of brahe who stated that the planets revolve around the sun 23. a system for organizing time