Charles Hakes Fort Lewis College1

Charles Hakes Fort Lewis College2 Chapter 3 Telescopes The Tools of Astronomy

Charles Hakes Fort Lewis College3 Charles Hakes Fort Lewis College3 Hotel Mauna Kea l

Charles Hakes Fort Lewis College4 Outline Test Friday Don’t forget your green/red scantron sheets #2 pencil(s). Calculator (no phone calculators) Optical Telescopes Refractors Reflectors Others Other Wavelengths

Charles Hakes Fort Lewis College5 Drop-in Study Sessions Thursday 2:30-4:30 Use it or lose it. Don’t forget conversion practice page Review questions on-line also

Charles Hakes Fort Lewis College6 Review What was the most important thing you learned? the speed of light, x-ray, gamma rays... is all the same. (~= 3.00x10 8 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 College7 Charles Hakes Fort Lewis College7 The Speed of Light 299, km/sec (~= 3.00x10 8 m/s) It’s not just a good idea. It’s the law!

Charles Hakes Fort Lewis College8 Charles Hakes Fort Lewis College8 History of The Speed of Light

Charles Hakes Fort Lewis College9 Charles Hakes Fort Lewis College9 Figure 2.4 Charged Particles

Charles Hakes Fort Lewis College10 Charles Hakes Fort Lewis College10 Figure 2.5 Magnetism

Charles Hakes Fort Lewis College11 Charles Hakes Fort Lewis College11 Figure 2.6 Electromagnetic Wave

Charles Hakes Fort Lewis College12 Charles Hakes Fort Lewis College12 Figure 2.7 Visible Spectrum

Charles Hakes Fort Lewis College13 Charles Hakes Fort Lewis College13 Figure 2.8 Electromagnetic Spectrum

Charles Hakes Fort Lewis College14 Which is correct A) period * frequency = wavelength B) velocity / period = wavelength C) velocity * frequency = wavelength D) velocity * period = wavelength

Charles Hakes Fort Lewis College15 Which is correct A) period * frequency = wavelength B) velocity / period = wavelength C) velocity * frequency = wavelength D) velocity * period = wavelength

Charles Hakes Fort Lewis College16 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 College17 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 College18 Discussion/Exercise What is the wavelength of a microwave oven at 2.45 GHz?

Charles Hakes Fort Lewis College19 What is the wavelength of a microwave oven at 2.45 GHz? A) 7.35x10 17 m B) m C) 122 m D) m

Charles Hakes Fort Lewis College20 Chapter 3 Hubble Space Telescope and VLT

Charles Hakes Fort Lewis College21 Figure 3.6bc Palomar Telescope

Charles Hakes Fort Lewis College22 Figure 3.8 Mauna Kea Observatory

Charles Hakes Fort Lewis College23 Figure 3.9 VLT Observatory

Charles Hakes Fort Lewis College24 Figure 3.X FLC Observatory

Charles Hakes Fort Lewis College25 Figure 3.X FLC Observatory

Charles Hakes Fort Lewis College26 Telescopes What is a telescope? What does it do for you?

Charles Hakes Fort Lewis College27 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 College28 Figure 3.1 Reflecting Mirror

Charles Hakes Fort Lewis College29 Figure 3.3 Image Formation

Charles Hakes Fort Lewis College30 Types of Telescopes Refractor Galilean Achromatic Apochromatic Reflector Newtonian Cassegrain Catadioptric Schmidt Cassegrain Maksutov Cassegrain

Charles Hakes Fort Lewis College31 Figure 3.4 Reflectors and Refractors

Charles Hakes Fort Lewis College32 Refractors

Charles Hakes Fort Lewis College33 Figure 3.2 Refracting Lens

Charles Hakes Fort Lewis College34 Figure 2.7 Visible Spectrum

Charles Hakes Fort Lewis College35 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 College36 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 College37 Demonstration Making a refractor telescope Objective Eyepiece Mount

Charles Hakes Fort Lewis College38 Reflectors Newtonian Parabolic mirror Several places possible to focus the light.

Charles Hakes Fort Lewis College39 Figure 3.5 Reflecting Telescopes

Charles Hakes Fort Lewis College40 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 College41 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 College42 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 College43 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 College44 Figure 3.7 Sensitivity Size does matter Bigger is better! (diameter, that is)

Charles Hakes Fort Lewis College45 Figure 3.6a Palomar Telescope

Charles Hakes Fort Lewis College46 Figure 3.6bc Palomar Telescope

Charles Hakes Fort Lewis College47 Figure 3.8 Mauna Kea Observatory

Charles Hakes Fort Lewis College48 Figure 3.9 VLT Observatory

Charles Hakes Fort Lewis College49 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 College50 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 College51 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 College52 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 College53 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 College54 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 College55 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 College56 Figure 3.10 Resolution

Charles Hakes Fort Lewis College57 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?