1. Type of reflecting telescope with a concave secondary mirror

2. Type of telescope that detects and analyzes radio waves from space

3. Tube attached to the front of the telescope to reduce condensation

4. Telescope that uses mirrors to gather and focus light

5. Vertical distance above a given level or surface

6. Devices used to adjust focus in the telescope

7. Grouping of stars forming a recognizable pattern

8. Small telescope or sight used to locate objects in the sky

9. Polished surface that reflects light to form an image

10. Interstellar clouds of gas and dust

11. Ability of a telescope mount to follow objects as they move

12. Group of galaxies held together by gravity

13. Point at which rays of light meet or intersect

14. Lens or group of lenses in the telescope that is closest to the eye

15. Piece of glass or other transparent material that focuses or disperses light

16. Mirror or prism used to divert the light path

17. Cover for one eye to improve vision through a telescope

18. Bend or change direction when passing through a medium