Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Charles Hakes Fort Lewis College 1 Chapter 3 Telescopes The Tools of Astronomy Charles Hakes Fort Lewis College 2 Hotel Mauna Kea http://www.youtube.com/watch?v=XPdTlHK1h_0 Charles Hakes Fort Lewis College 3 Outline • Grades posted • Test Friday • Don’t forget your red scantron sheets • #2 pencil(s). • Calculator (no phone calculators) • Optical Telescopes • Refractors • Reflectors • Others • Other Wavelengths Charles Hakes Fort Lewis College 4 Review • What was the most important thing you learned? • the speed of light, x-ray, gamma rays... is all the same. (~= 3.00x108 m/s) • wavelength x frequency = velocity • frequency = 1/period • Electromagnetic waves don’t need anything to move in. • There are far more types of invisible “light” than there are visible Charles Hakes Fort Lewis College 5 The Speed of Light 299,792.458 km/sec (~= 3.00x108 m/s) It’s not just a good idea. It’s the law! Charles Hakes Fort Lewis College 6 Figure 2.8 Electromagnetic Spectrum Charles Hakes Fort Lewis College 7 Which is correct A) B) C) D) Charles Hakes Fort Lewis College period * frequency = wavelength velocity / period = wavelength velocity * frequency = wavelength velocity * period = wavelength 8 Which is correct A) B) C) D) Charles Hakes Fort Lewis College period * frequency = wavelength velocity / period = wavelength velocity * frequency = wavelength velocity * period = wavelength 9 Which list is in the correct order of electromagnetic radiation frequency, going from lowest to highest? A) infrared, ultraviolet, gamma, radio B) gamma, x-ray, ultraviolet, visible C) radio, infrared, visible, ultraviolet D) radio, x-ray, ultraviolet, visible E) red, violet, blue, green Charles Hakes Fort Lewis College 10 Which list is in the correct order of electromagnetic radiation frequency, going from lowest to highest? A) infrared, ultraviolet, gamma, radio B) gamma, x-ray, ultraviolet, visible C) radio, infrared, visible, ultraviolet D) radio, x-ray, ultraviolet, visible E) red, violet, blue, green Charles Hakes Fort Lewis College 11 Discussion/Exercise • What is the wavelength of a microwave oven at 2.45 GHz? Charles Hakes Fort Lewis College 12 What is the wavelength of a microwave oven at 2.45 GHz? A) B) C) D) 7.35x1017 m 0.735 m 122 m 0.122 m Charles Hakes Fort Lewis College 13 Chapter 3 Hubble Space Telescope and VLT Charles Hakes Fort Lewis College 14 Figure 3.6bc Palomar Telescope Charles Hakes Fort Lewis College 15 Figure 3.8 Mauna Kea Observatory Charles Hakes Fort Lewis College 16 Figure 3.9 VLT Observatory Charles Hakes Fort Lewis College 17 Figure 3.X FLC Observatory Charles Hakes Fort Lewis College 18 Figure 3.X FLC Observatory Charles Hakes Fort Lewis College 19 Telescopes • What is a telescope? • What does it do for you? Charles Hakes Fort Lewis College 20 Telescopes • A telescope is a “light bucket” - it gathers photons. • A telescope is an imaging device - it focuses the photons. • It also magnifies, but this is less important. Charles Hakes Fort Lewis College 21 Figure 3.1 Reflecting Mirror Charles Hakes Fort Lewis College 22 Figure 3.3 Image Formation Charles Hakes Fort Lewis College 23 Types of Telescopes • Refractor • Galilean • Achromatic • Apochromatic • Reflector • Newtonian • Cassegrain • Catadioptric • Schmidt Cassegrain • Maksutov Cassegrain Charles Hakes Fort Lewis College 24 Figure 3.4 Reflectors and Refractors Charles Hakes Fort Lewis College 25 Refractors Charles Hakes Fort Lewis College 26 Figure 3.2 Refracting Lens Charles Hakes Fort Lewis College 27 Figure 2.7 Visible Spectrum Charles Hakes Fort Lewis College 28 Refractors • Galilean • Uses one positive and one negative lens. • No longer made. (except for toys = “pirate” telescope) • Very narrow field of view • Achromatic • Apochromatic Charles Hakes Fort Lewis College 29 Refractors • Achromatic • • • • Most common type of small telescope today. The “objective” lens has two different types of glass. Red light and green light can focus in the same spot. Often have a “purple haze” on bright objects. • Apochromatic • Uses exotic glass or more than two lens elements. • Gets three of more colors to focus together - no more purple haze • Expensive. Charles Hakes Fort Lewis College 30 Demonstration • Making a refractor telescope • Objective • Eyepiece • Mount Charles Hakes Fort Lewis College 31 Reflectors • Newtonian • Parabolic mirror • Several places possible to focus the light. Charles Hakes Fort Lewis College 32 Figure 3.5 Reflecting Telescopes Charles Hakes Fort Lewis College 33 Reflectors • Assembly Demonstration • Advantages • can make mirrors bigger (can support them from the back) • Reflection only on surface (colors focus together) • Only need one optical surface (lenses require at least two) Charles Hakes Fort Lewis College 34 Telescopes • Building your own telescope can be very fun and rewarding. • You cannot build a telescope as cheaply as you can buy one. • Be sure to get good eyepieces. Half the imaging device is the eyepiece. Some can be expensive, however. Charles Hakes Fort Lewis College 35 Telescopes • No telescope is good at all things. • Know what you want to observe. • The best telescope is the one that gets used the most. Charles Hakes Fort Lewis College 36 Useful Parameters • Focal ratio (focal length/diameter) • Magnification (FL/fl) • maximum 50x/inch rule of thumb • or… 300x max (from the atmosphere) • Exit pupil (diameter/magnification) • 7mm max • 0.5mm min Charles Hakes Fort Lewis College 37 Figure 3.7 Sensitivity •Size does matter •Bigger is better! (diameter, that is) Charles Hakes Fort Lewis College 38 Figure 3.6a Palomar Telescope Charles Hakes Fort Lewis College 39 Figure 3.6bc Palomar Telescope Charles Hakes Fort Lewis College 40 Figure 3.8 Mauna Kea Observatory Charles Hakes Fort Lewis College 41 Figure 3.9 VLT Observatory Charles Hakes Fort Lewis College 42 Telescope size • Light gathering ability is proportional to the area of the objective. • This means it is proportional to the diameter squared. • 8” telescope gathers 4 times the light of a 4” telescope. ( 8”x8”=64 sq in, 4”x4”=16 sq in ) • Photographic exposures would be 1/4 as long on the 8” as they would be on the 4” • Similarly, an 8” telescope gathers 1/4 as much light as a 16” telescope. Charles Hakes Fort Lewis College 43 Size Example - Binoculars • 10x50 binoculars • “10” means • “50” means - • How much more light can they gather than your naked eye? • eyes ~7mm diameter Charles Hakes Fort Lewis College 44 Size Example - Binoculars • 10x50 binoculars • “10” means - magnification • “50” means - • How much more light can they gather than your naked eye? • eyes ~7mm diameter Charles Hakes Fort Lewis College 45 Size Example - Binoculars • 10x50 binoculars • “10” means - magnification • “50” means - diameter in mm • How much more light can they gather than your naked eye? • eyes ~7mm diameter Charles Hakes Fort Lewis College 46 Size Example - Binoculars • 10x50 binoculars ~50x area of pupil. • To get another 50x light gathering power, you would need ~14” diameter telescope! Charles Hakes Fort Lewis College 47 A 5 meter (diameter) telescope A) gathers 5 times as much light as a 1 m telescope B) gathers 1/2 as much light as a 10 m telescope C) gathers 4 times as much light as a 2.5 m telescope D) gathers 5/2 as much light as a 2 m telescope Charles Hakes Fort Lewis College 48 A 2 meter telescope takes a picture of a galaxy in 10 minutes. How long will it take to make the same exposure using a 1 meter telescope? A) 5 minutes B) 2.5 minutes C) 20 minutes D) 40 minutes Charles Hakes Fort Lewis College 49 Figure 3.10 Resolution Charles Hakes Fort Lewis College 50 Three Minute Paper • Write 1-3 sentences. • What was the most important thing you learned today? • What questions do you still have about today’s topics? Charles Hakes Fort Lewis College 51