Visible

• What Your Eyes See:The human eye only sees visible light. Sometimes scientists call this the optical range of light. This has been the most studied wavelength. Astronomers will often work in the "blue end" if they are interested in slightly hotter stars or the "red end" for cooler ones.
• What are Good Sources of Visible Light? When a star ages, its outer envelope can expand to 50 times its normal size. When it expands, it cools and looks red. It is then called a "red-giant" star. You can see that stars have different colors by looking at the constellation Orion this Fall. The star to the north is the red-giant Betelgeuse, compare how it looks to the star in the lower right corner of Orion, which is Rigel a hotter younger star. Other objects frequently observed in visible light are the Moon, solar system objects (Mars, Venus, our Sun, etc.), stars, and other galaxies.
• Of course, we see all sorts of things on Earth. The Sun's light we see reflected off of objects on Earth is visible light. Because visible light reaches us, we can observe objects like the Sun, the Moon, planets, and stars from ground-based telescopes. Some famous visible light telescopes are, Keck Telescope in Hawaii, Kitt Peak National Observatory in Arizona, and Cerro Tololo Inter-American Observatory in Chile
• Here's Some Easy-To-Do Visible Light Activities at the Exploratorium. (Will appear in your second window)

• Keck Observatory atop Mauna Kea on the Big Island of Hawaii. The Keck Telescope is eight stories tall and 300 tons in weight.