astronomical observations typeatmosphere radio wavesno effect microwavesmostly blocked ...
DESCRIPTION
Eye Object Focal Plane Lens Working in reverse, a lens can magnify a small object making it look big and far away The closer the focal plane is, the bigger the image You can also magnify an image Lenses and LightTRANSCRIPT
Astronomical Observations
Type AtmosphereRadio Waves No effectMicrowaves Mostly blockedInfrared BlockedVisible Light Slight blurringUltraviolet BlockedX-rays BlockedGamma Rays Blocked
What wavelengths to use?
Incoming Rays
Lens
Outgoing Rays
Focal Plane
Image
Lenses and Light
Light waves going through a lens are bentThey converge on the focal plane of the lensAn image forms on the focal planeThe greater the distance to the focal plane, the bigger the image
EyeObject
Focal Plane
Lens
Working in reverse, a lens can magnify a small object making it look big and far awayThe closer the focal plane is, the bigger the imageYou can also magnify an image
Lenses and Light
EyeFrom Point Source 2
From Point Source 1
Objective Lens Eyepiece
Focal Plane
Two lenses together make a telescopeChanging the eyepiece changes the magnificationThe amount of light gathered depends on the size of the objective
Image of Point 1
Image of Point 2
Lenses and Light
PrismView directlyCCD cameraSpectrometer
The Spectrometer•Uses prism or (more likely) diffraction grating•Breaks light into different colors/wavelengths/frequencies
From the Telescope
What to do with the light
CCD detector
Mirrors and Light
Mirrors can also create images - in some ways, better than lensesLarge telescopes are always reflectors
Focal Plane
MirrorIncoming Rays
Reflected Rays
The largest optical telescopes in the worldGran Telescopio Canarias
10.6 m diameterKeck 1 and Keck 2
10 m diameter each
What makes a good telescopeThe bigger the diameter, the better
Bigger diameter = more light gathering powerBigger diameter = less diffraction (blurring)
Avoid atmospheric distortion and light pollutionSpaceMountainsAway from light pollution
Magnification is not the main issueEyepiece changes magnification
Outside the solar system, you can never decrease the distance
Too far away
Space Based TelescopesSeveral advantages of going to space
No atmospheric distortionNo light pollutionCan see infrared/ultraviolet
Hubble Telescope James Webb Space TelescopeLaunches 2018
Active Optics
It is hard to make large mirrorsIt is easier to make several small mirrorsYou can use motors & computer to line them up
Focal Plane
Mirror
Incoming Rays
Reflected Rays
Adaptive Optics
Light gets distorted by the atmosphereIt ends up imperfect at the telescopeThis ruins the focus, blurring the image
Focal Plane
Mirror
Computers can respond to imperfectionsMotors can adjust the mirrorsThis fixes the blurred image
Focal PlaneMirror
Adaptive Optics
Telescopes are used here on earth to observe visible light from space. Why aren’t they used for infrared and ultraviolet light?A) No astronomical objects produce these kinds of lightB) The atmosphere blocks these types of lightC) No mirrors or lenses have ever been discovered that can reflect/refract these kinds of lightD) Film and CCD cameras can’t detect these types of light
What wavelengths to use?
What wavelengths to use?
Type AtmosphereRadio Waves No effectMicrowaves Mostly blockedInfrared BlockedVisible Light Slight blurringUltraviolet BlockedX-rays BlockedGamma Rays Blocked
Radio Telescopes
Reflector
Incoming Radio Waves
Reflected Radio Waves
Antenna
Always use a radio reflector (like a mirror)High precision reflector is not necessary because radio waves are very longMost radio sources are quite weak
Arecibo Telescope, 305 m
Robert C. Byrd Green Bank Telescope, about 100 m
Radio Telescopes
Radio Interferometry
No atmospheric blurringBackground ProblemHuge diffraction limit problem (about 1o)Signal can be combined from multiple radio telescopesEffective size is distance between telescopesEffective resolution better than optical
Radio Interferometry
Very Large Array
Radio Interferometry
Very Long Baseline Array
What wavelengths to use?
Mostly restricted to spaceLimited microwave and IR from Earth
Type AtmosphereRadio Waves No effectMicrowaves Mostly blockedInfrared BlockedVisible Light Slight blurringUltraviolet BlockedX-rays BlockedGamma Rays Blocked
Infrared and Microwave Space TelescopesSpitzer Space
Telescope
Herschel Observatory
Wilkinson Microwave Anisotropy Probe
Planck Observatory
X-Ray Space TelescopesChandra X-Ray Observatory
XMM Newton
Rossi X-Ray Timing Explorer
Swift Gamma Ray Burst Telescope
UV and Gamma-Ray Space Telescopes
GALEXINTEGRAL
Fermi Gamma-Ray Space Telescope