Telescopes

1. Telescopes Chapter 5

2. What do you think of when someone asks you about a telescope?

3. Types of telescopes • Interferometers (not a type of telescope, but decrease light interference) • Radio telescopes

4. Telescopes • The most basic telescopes work by gathering light, then focusing and/or “bending light” onto a particular spot. • This causes an increase in the magnification of an image.

5. Determining a good telescope • – how much more light that a telescope can gather than the human eye. • The larger the lens, the more collecting power. • This allows for a brighter image (easier for you to see) • Telescopes are first described by the diameter of its light collecting device (mirror or lens) • Once light is collected then it must be focused.

6. Determining a good telescope • How light is focused • – Light is focused to form a particular image using a lens. • Relies on the process of which is the bending of light when it goes through different media. Occurs because the speed of light changes when it enters the lens. • Refraction also spreads the light out. Results in the colors of the rainbow. • – The spreading of light or other electromagnetic radiation into a spectrum. • The light rays are bent when they go through one media (air) and then another (glass)

7. Refracting Telescopes • Use lenses to focus light • Are limited by the size and quality of the lens. • Most modern telescopes are reflecting telescopes as opposed to refracting telescopes. • We will make a refracting telescope in class this week.

8. Reflecting telescopes • Use reflectors to collect and focus light. • are slightly curved mirrors • Light does not go through them and as a result is not dispersed. • Most telescopes today are reflecting • Multiple mirrors bounce the light around, each time bending it slightly and thus magnifying the image.

9. Atmospheric Refraction • Occurs for objects viewed in the sky. • The gases of the atmosphere bend light and change the appearance of an object • refraction makes the sun look higher in the sky than it really is. • Atmospheric refraction is stronger closer to the horizon. Causes the sun to look flat as it sets.

10. Determining a good telescope • Besides collecting light, telescopes also allow us to discern objects as single large object or several small individuals • – The ability of a telescope or instrument to discern fine details. Larger diameter telescopes have greater resolving power than smaller ones. • Resolving power is limited because light waves can be diffracted. • Diffraction – • Diffraction limits the resolving power of a telescope.

11. Interferometers • A device consisting of two or more telescopes connected together to work as a single instrument. • Allow for a high resolving power, the ability to see small scale features. • Can be used to increase the power of radio, infrared, and visible wavelengths.

12. Observatories • As far as telescopes discussed by the groups, for the test, make sure to look over the telescopes and observatories discussed in the book. • Remember that SEVERAL telescopes are located in Hawaii (Mauna Kea) • Why are so many telescopes in HI? • Cleaner air, less pollution, and relatively high elevation.

13. Non optical telescopes • Most X rays and UV light is absorbed by the atmosphere. • Radio waves can penetrate the atmosphere. • Gamma ray telescopes measure gamma rays that are released during nuclear explosions. • These explosions occur during stellar evolution.