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AstronomicalObservingTechniques Lecture3:EyestotheSkies ChristophU.Keller [email protected] Outline 1. Poin8ngTelescopesonEarth 2. SpaceTelescopeOrbits 3. Op8calTelescopes 4. RadioTelescopes,Interferometers 5. X-rayandGamma-RayTelescopes 6. NeutrinoTelescopes 7. Gravita8onalWaveTelescopes 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 2 EarlyTelescopes • HansLipperhey1608: spyglasses • GalileoGalilei1609: firstuseinastronomy • Kepler1611: improvedrefractor 15-2-2016 Newton1668: firstreflector Herschel1789: 1.22-mdiameter,12-m long Astronomical Observing Techniques 2016: Telescopes 3 TelescopeMounts Equatorialmount Azimuthalmount +singlemovingaxis +constantrota8on +noimagerota8on -large,heavy -instruments:varyinggravity 15-2-2016 +lightandsymmetric +fixedgravityonbearings +twofixed-gravityports -twomovingaxes -imagerota8on Astronomical Observing Techniques 2016: Telescopes 4 CTIO 4-m, www.noao.edu/image_gallery/html/im0132.html 15-2-2016 WIYN 3.5-m www.noao.edu/image_gallery/html/im0525.html Astronomical Observing Techniques 2016: Telescopes 5 Azimuthal Telescope Mounts SALT VLT www.eso.org/public/archives/images/screen/vlt-Inside-c-cc.jpg 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 6 SpaceTelescopeOrbits Orbitchoiceinfluencedby Orbits - lowEarth - sun-synchronous - geosta8onary - Earth-trailing - L2 - - - - - HST : low Earth orbit ~96 minutes 15-2-2016 communica8ons thermalbackgroundradia8on spaceweather skycoverage access(servicing) Spitzer: Earth-trailing solar orbit ~60 yr Astronomical Observing Techniques 2016: Telescopes 7 LagrangianPoints map.gsfc.nasa.gov/mission/observatory_l2.html 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 8 L2 JWST,WMAP,GAIA,HerschelinorbitsaroundL2 +sun-shields -orbitaroundL2 -radia8on 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 9 TelescopeOp@cs Scale: tan ω = l f Magnifica8on: f1 D1 ω2 V= = = f 2 D2 ω1 15-2-2016 and for small ω : l ≈ 0.0175ωf Astronomical Observing Techniques 2016: Telescopes 10 Hollandsche Kijker entrance pupil f1 f2 magnifica8on=f1/f2 limitations: field, chromatic aberrations 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 11 Kepler Refractor • larger FOV • image upside down f1 f2 magnifica8on=f1/f2 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 12 SphericalLenses Spherical Aberration: Beams away from center have shorter focal lengths 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 13 SphericalMirrors • providelargefieldof view(FoV) • raysmoredistantfrom op8calaxishavea differentfocalpoint 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 14 ParabolicMirrors Parabolicprimarymirrorsfocusallraysfromthesamedirec8onto onepoint. But:differentdirec8onshavedifferentfocalpoints. v àFieldofviewlimitedbyaberra8ons:thebiggerthemirrorthe biggerthedifference[parabola–sphere]neartheedgeàbigger telescopeshavesmallerFOVs(~<1deg) 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 15 SchmidtTelescope Idea: 1. Usesphericalprimarymirrorfor maximumfieldofview(>5deg)ànooffaxisasymmetrybutsphericalaberra8ons 2. correctsphericalaberra8onswith correctorlens. TwometerAlfred-JenschTelescopeinTautenburg,the largestSchmidtcamerainthe world. 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 16 Two-MirrorTelescopes Newtonian 15-2-2016 Cassegrain Gregorian Three Mirror Anastigmat (TMA) Astronomical Observing Techniques 2016: Telescopes 17 Ritchey-Chré@enConfigura@on Modifica8onofCassegrainconfigura8on(parabolicprimary,ellip8cal secondary):Hyperbolicprimarymirror(almostparabola)andhyperbolic secondarymirroreliminates(some)op8calerrors(3rdordercomaandspherical aberra8on). à largefieldofview&compactdesign(foragivenfocallength) 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 18 Ritchey-Chrétien Telescopes VLT (4x) GTC 15-2-2016 Subaru Keck (2x) Astronomical Observing Techniques 2016: Telescopes Gemini (2x) 19 Ritchey-Chrétien Telescope HST 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 20 TMA Wide-Field Telescope Large Synoptic Survey Telescope (LSST) 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 21 LightGatheringPowerandResolu@on Lightgatheringpower 2 ⎛D⎞ Forextendedobjects: S / N ∝ ⎜⎜ ⎟⎟ (seelectureonS/N) ⎝ f ⎠ S / N ∝ D2 Forpointsources: λ fλ Angularresolu8on sin Θ = 1.22 or Δl = 1.22 D D (givenbytheRayleighcriterion) 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 22 TelescopeFoci–wheretoputtheinstruments Primefocus–widefield,fastbeambutdifficultto accessandnotsuitableforheavyinstruments Cassegrainfocus–moveswithtelescopes,small field 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 23 TelescopeFoci–wheretoputinstruments(2) Nasmyth–idealforheavyinstrumentsto putonastableplarorm,butfieldrotates Coudé–veryslowbeam,usuallyforlarge spectrographsinthe“basement” 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 24 GrowthofTelescopeCollec@ngArea sin Θ = 1.22 15-2-2016 λ D Astronomical Observing Techniques 2016: Telescopes 25 MassLimita@ons biggermirrorsrequire • thinner/segmentedmirrors • ac8vesupport 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 26 Segmented,ThinandHoneycombMirrors 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 27 Ac@veMirrorSupport 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 28 Op@calTelescopesinComparison 15-2-2016 Palomar Keck JWST Telescopeaperture 5m 10m 6.5m Telescopemass 600t 300t 6.5t #ofsegments 1 36 18 Segmentsize 5m 1.8m 1.3m Mass/segment 14’500kg 400kg 20kg Astronomical Observing Techniques 2016: Telescopes 29 RadioTelescopes Arecibo, Puerto Rico – the largest Dishes similar to optical telescopes (305m) single-aperture telescope but with much lower surface accuracy Effelsberg, Germany – 100m fully steerable telescope Greenbank, USA – after structural collapse (now rebuilt) 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 30 ArraysandInterferometers VLA in New Mexico – 27 antennae (each 25m) in a Y-shape (up to 36 km baseline) WSRT (Westerbork) in Drenthe – 14 antennae along 2.7 km line ALMA in Chile – 50 dishes (12m each) at 5000m altitude 400µm – 3mm (720 GHz – 84GHz) LOFAR in the Netherlands • LOwFrequencyARrayusestwotypesoflowArecibo costantennae: • LowBandAntenna(10-90MHz) • HighBandAntenna(110-250MHz). • Antennaeareorganizedin36sta8ons • over~100km.Eachsta8oncontains • 96LBAsand48HBAs • Baselines:100m–1500km • MainLOFARsubsystems: • sensorfields • wideareanetworks • centralprocessing systems • userinterfaces X-rayTelescopes • X-raysimpingingperpendicularonanymaterialarelargelyabsorbed ratherthanreflected • telescopeop8csbasedonglancinganglereflec8on(ratherthan refrac8onorlargeanglereflec8on) • typicalreflec8ngmaterialsforX-raymirrorsaregoldandiridium (goldhasacri8calreflec8onangleof3.7degat1keV). Gamma-RayTelescopes FERMI satellite Fig. 1 in arxiv.org/pdf/0902.1089v1.pdf 15-2-2016 MAGIC Cerenkov telescopes magic.mpp.mpg.de/newcomers/introduction/ Astronomical Observing Techniques 2016: Telescopes 34 RHESSIGamma-Ray hesperia.gsfc.nasa.gov/rhessi3/ mission 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 35 NeutrinoTelescopes neutrino.kek.jp/figures.html Super-Kamiokande, 50,000 tons of water 15-2-2016 www.sno.phy.queensu.ca/sno/ images Sudbury Neutrino Observatory, 1000 tons of D2O Astronomical Observing Techniques 2016: Telescopes 36 NeutrinoDetec@on • scaxeringofneutrinos onelectrons:e-+νeè e-+νe • electronacceleratedto v>cèCerenkov radia8on • solarneutrinos • neutrinooscilla8ons • neutrinosfrom SN1987A 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 37 NeutrinosinIceandWater gallery.icecube.wisc.edu IceCube at the South Pole 15-2-2016 antares.in2p3.fr/Gallery ANTARES in Mediterranean Sea Astronomical Observing Techniques 2016: Telescopes 38 Gravita@onalWaveDetectors ligo.org/multimedia/gallery 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 39 GWMeasurementPrinciple ligo.org/science/GW-Overview/images/IFO.jpg 15-2-2016 Astronomical Observing Techniques 2016: Telescopes 40