How did ancient people use observatories? -- Focus on: ancient observatories -- Focus on: Chichén Itzá: architecture and the gods -- How do modern observatories differ from ancient observatories? -- Why are many observatories round with a dome? -- Why are many observatories on mountains? -- What kinds of telescopes are used in observatories? -- How far out in space and back in time can telescopes see? -- What do astronomers study using ground-based observatories? -- What is an optical telescope? -- Focus on: Keck Observatory: at the edge of the heavens -- What are magnification and resolving power? -- Who invented the first optical telescopes? -- Focus on: new moons, new wonders -- How does a refracting telescope work? -- Focus on: the pursuit of light -- Who invented the first reflecting telescope? -- How does a reflecting telescope work? -- How does a reflecting-refracting telescope work? -- How do telescopes make images? -- How do astronomers use computers to create astronomical images? -- Why are there different types of telescope mirrors? -- What is light pollution? -- What have ground-based observatories taught us about the solar system? -- What have ground-based observatories taught us about the larger universe? -- Focus on: Kitt Peak Observatory: an astronomical oasis -- What does the future hold for ground-based observatories?