Overview:Observing Techniques&Typesamedling/obstech/obstech_2_telescopes.pdf · Sciencecasesbywavelength Regime& Wavelength(nm)& Approximate& Blackbody& Temperature SomeCommon Sources

Overview: Observing Techniques & Types 24 February 2016

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

Observatories across the EM spectrum

•  Blah blah

Image: STScI/JHU/NASA

Why do we send telescopes to space? •  The atmosphere absorbs all/most of the photons at some wavelengths

Image: STScI/JHU

/NAS

A

Atmospheric Absorption

Image: STScI/JHU

/NAS

A

Atmospheric Absorption

This is never zero – always need to calibrate!

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

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

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

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

Movie: C

. Max, Cen

ter for Adap;

ve Op;

cs

Optical ConFigurations

Prime Focus

Cassegrain

Coudé or Nasmyth


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)


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

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




•  Interferometry •  Combine light from mul;ple telescopes •  Resolu;on set by distance between them

•  Polarimetry •  Only observe waves polarized by e.g. dust scanering

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

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

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)

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!

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)

Observing Modes: Pros and cons •  Guest Observer

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



•  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



•  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!

Documents

Overview:Observing Techniques&Typesamedling/obstech/obstech_2_telescopes.pdf · Sciencecasesbywavelength Regime& Wavelength(nm)& Approximate& Blackbody& Temperature SomeCommon Sources