overview:observing techniques&typesamedling/obstech/obstech_2_telescopes.pdf ·...
TRANSCRIPT
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Overview: Observing Techniques & Types 24 February 2016
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Science cases by wavelength Regime Wavelength (nm) Approximate
Blackbody Temperature
Some Common Sources
Gamma rays <0.01 > 108 K Some nuclear reac;ons
X-‐rays 0.01-‐20 106 – 108 K AGN, gas in galaxy clusters, supernova remnants, solar corona
Ultraviolet 20-‐400 105 – 106 K Supernova remnants, very hot stars (recent star forma;on)
Visible 400-‐700 103 – 105 K Stars, hot (104 K) gas
Infrared 103 -‐ 106 10 -‐ 103 K Warm clouds of dust and gas, planets
Radio > 106 < 10 K Dust, cold gas
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Observatories across the EM spectrum
• Blah blah
Image: STScI/JHU/NASA
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Why do we send telescopes to space? • The atmosphere absorbs all/most of the photons at some wavelengths
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Image: STScI/JHU
/NAS
A
Atmospheric Absorption
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Image: STScI/JHU
/NAS
A
Atmospheric Absorption
This is never zero – always need to calibrate!
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Why do we send telescopes to space? • The atmosphere absorbs all/most of the photons at some wavelengths
• Atmospheric turbulence blurs images • “Seeing” = size of a point source in arcseconds; depends on site and weather
• 0.5” in the best condi;ons, 3-‐5” in bad condi;ons
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Atmospheric blurring
• Speckled point spread func;on + image mo;on • Averages out to a Gaussian “seeing disk”
Movie: C. Max, Center for Adap;ve Op;cs
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In space, diffraction-‐limited • Light wave interference causes diffrac;on, which dictates the point spread func;on • PSF is the Fourier Transform of your pupil (mirror) • Resolu;on ~ λ/D
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Adaptive Optics • Measure turbulence in the atmosphere and correct the blurring • Achieve diffrac;on-‐limited imaging from the ground • Much cheaper than flying to space!
Image: C. Max, Center for Adap;ve Op;cs
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Movie: C
. Max, Cen
ter for Adap;
ve Op;
cs
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Optical ConFigurations
Prime Focus
Cassegrain
Coudé or Nasmyth
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Optical ConFigurations
Prime Focus
Cassegrain
Coudé or Nasmyth In pairs: what are some reasons why a design team might
choose to put a camera at one focus versus another?
(4 min)
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Optical ConFigurations
Prime Focus Widest field of view, highest throughput
Cassegrain For instruments too large to sit at PF
Coudé or Nasmyth For instruments that can’t move with the telescope
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Types of Data • Images • Morphology, sizes, colors
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Types of Data • Images • Morphology, sizes, colors
• Spectroscopy • Chemical abundances, stellar popula;ons • Emission/absorp;on line analysis • Kinema;c informa;on
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Types of Data • Images • Morphology, sizes, colors
• Spectroscopy • Chemical abundances, stellar popula;ons • Emission/absorp;on line analysis • Kinema;c informa;on
• Integral-‐Field Spectroscopy • Resolved spectroscopy: mapping above
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Types of Data • Images • Morphology, sizes, colors
• Spectroscopy • Chemical abundances, stellar popula;ons • Emission/absorp;on line analysis • Kinema;c informa;on
• Integral-‐Field Spectroscopy • Resolved spectroscopy: mapping above
• Interferometry • Combine light from mul;ple telescopes • Resolu;on set by distance between them
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Types of Data • Images • Morphology, sizes, colors
• Spectroscopy • Chemical abundances, stellar popula;ons • Emission/absorp;on line analysis • Kinema;c informa;on
• Integral-‐Field Spectroscopy • Resolved spectroscopy: mapping above
• Interferometry • Combine light from mul;ple telescopes • Resolu;on set by distance between them
• Polarimetry • Only observe waves polarized by e.g. dust scanering
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Telescopes with ANU Access • 2.3-‐meter at Siding Spring (RSAA TAC) • WiFeS op;cal integral field spectrograph (medium resolu;on, R~3000-‐7000)
• Op;cal imager • Echelle op;cal spectrograph (high resolu;on, R~24,000)
• Skymapper (RSAA TAC) • 1.3m telescope with 5.7 sq degree field of view; uvgriz+Hα
• Keck Observatory, 10-‐m telescopes (KTAC: Aus-‐wide) • Op;cal and near-‐infrared imaging • Op;cal and near-‐infrared spectroscopy (longslit and mul;plexed)
• Near-‐IR integral field spectroscopy • AO in the near-‐IR
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Telescopes with Australian Access • AAT 4-‐m telescope (ATAC) • Op;cal spectroscopy: high resolu;on and moderate resolu;on mul;-‐object; integral field spectroscopy
• Near-‐IR imaging/moderate res spectroscopy • Gemini N+S 8-‐m telescopes (ATAC) • Op;cal and near-‐IR imaging, spectroscopy, IFU; AO in the near-‐IR
• Australia has a 7 nights in 2016; not clear for 2017 and beyond; classical observing only
• Magellan 6.5-‐m telescopes (ATAC) • Op;cal and NIR imaging and spectroscopy • MagAO – correc;on in NIR and op;cal images simultaneously
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Telescopes with Australian Access • Las Cumbres Observatory Global Telescope network: • 9 1-‐m telescopes (imaging) ; 2 2-‐m telescopes (imaging + low-‐res spectroscopy)
• Radio telescopes (ATNF TAC) • Australia Telescope Compact Array (1.1-‐105 GHz, 6km) • Parkes (0.7-‐22 GHz, 64-‐m single dish) • Australian Long Baseline Array -‐> VLBI (1.65 – 8.4 GHz, up to 0.0038” resolu;on!)
• Tidbinbilla 70-‐m and 34-‐m antennas (1.65-‐22 GHz and 32GHz, single dish)
• Mopra (16-‐116 GHz; 22-‐m single dish) • Murchison Widefield Array (80-‐300 MHz; MWA TAC)
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Telescopes with Australian Access
• Also note that many interna;onal observatories have “guest observer” programs so you can apply from anywhere! • ESO observatories • NASA space observatories • ALMA
• But – “open skies” ;me is limited!
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Observing Modes • Guest Observer: “scheduled” • You stay awake all night and control the telescope / camera • Can be in person or remote
• Queue / Script-‐based: “service” • You submit scripts in advance • Your proposal is ranked and the computer or a support astronomer picks according to priori;es
• You get an email when the data are ready • Archival Data • You comb through data archives and use what’s available
• Target of Opportunity • You interrupt someone else for an unpredictable short-‐lived event (e.g. gamma-‐ray burst)
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Observing Modes: Pros and cons • Guest Observer
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Observing Modes: Pros and cons • Guest Observer • Pro: On-‐the-‐fly adjustments; can change science plan based on recent developments
• Con: Bad weather is your loss
• Queue / Script-‐based
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Observing Modes: Pros and cons • Guest Observer • Pro: On-‐the-‐fly adjustments; can change science plan based on recent developments
• Con: Bad weather is your loss
• Queue / Script-‐based • Pro: Can op;mize program based on condi;ons; cheaper • Con: You don’t know if your script is wrong un;l awer its too late
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Observing Modes: Pros and cons • Guest Observer • Pro: On-‐the-‐fly adjustments; can change science plan based on recent developments
• Con: Bad weather is your loss
• Queue / Script-‐based • Pro: Can op;mize program based on condi;ons; cheaper • Con: You don’t know if your script is wrong un;l awer its too late
But you rare
ly get to ch
oose!