Optical and NearInfrared Astronomical Instrumentation

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Optical and Near-Infrared Astronomical
Instrumentation

• Astronomy Instrumentation Postgraduate Course
• Richard Myers r.m.myers_at_durham.ac.uk
• Jürgen Schmoll jurgen.schmoll_at_durham.ac.uk
• Tim Morris t.j.morris_at_durham.ac.uk
• Tim Butterley timothy.butterley_at_durham.ac.uk
• Ali Basden a.g.basden_at_durham.ac.uk
• David Robertson d.j.robertson_at_durham.ac.uk

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Course Overview

• Introductory lectures (Shared with Astronomy PG
  course)
• Lecture 1. Telescopes Facilities, Thu 13 Nov -
  Dr. Richard Myers
• Lecture 2. Detectors, Tue 18 Nov (time to be
  re-arranged) - Dr. Alastair Basden
• Lecture 3. Imagers, Thu 20 Nov - Dr. Juergen
  Schmoll
• Lecture 4. Spectroscopy, Tue 25 Nov - Dr. Juergen
  Schmoll
• Lecture 5. Introduction to Adaptive Optics, Thu
  27 Nov - Dr. Tim Morris
• Advanced lectures (in Room 253)
• Lecture 6. Advanced Spectrograph Systems, Tue 2
  Dec - Dr. Juergen Schmoll
• Lecture 7. Interferometers, Thu 4 Dec (time to be
  re-arranged) - Dr. Alastair Basden
• Lecture 8. Advanced adaptive Optics Systems, Tue
  9 Dec - Dr. Tim Butterley
• Lecture 9. Space Optical/Near-IR Instrumentation,
  Thu 11 Dec - Dr. Juergen Schmoll
• Lecture 10. Tour of NetPark Research Institute,
  Tue 16 Dec - Mr. David Robertson
• (time and transport arrangements to be confirmed)

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Books
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Wavelength Ranges
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Available Facilities

• Funding most UK astronomical research is funded
  by STFC http//www.stfc.ac.uk/
• Major Optical/Near-IR Facilities in which the UK
  has a part-share
• AAO http//www.aao.gov.au/
• ING http//www.ing.iac.es/
• UKIRT http//www.jach.hawaii.edu/UKIRT/
• Gemini http//www.gemini.edu/
• ESO http//www.eso.org/
• HST http//www.stsci.edu/hst/

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Anglo-Australian Observatory

• The Anglo-Australian Observatory at Siding Spring
  Mountain in Australia consists of two telescopes
  
• The 3.9m diameter Anglo-Australian Telescope
  (AAT)
• broad range of common-user instrumentation for
  observations in the optical and near infra-red
  wavebands.
• STFC is an equal partner in the AAO with the
  Australian Research Council

• The UK Schmidt Telescope (UKST) concentrates on
  high-resolution wide-area sky surveys, originally
  through the use of large photographic plates and
  films, but now through spectral surveys with
  fibre feed (6dF).

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AAO instrumentation

• AAOmega new AAT optical spectrograph
• for 2 degree field 2df prime focus robotic fibre
  system and SPIRAL Cassegrain fibre integral field
  unit.
• IRIS2 - IR imager spectrograph
• 1024x1024 HgCdTe JHK imager / spectrograph
• Uni. College London Coudé Echelle Spectrograph
  (UCLES)
• Ultra High Resolution Facility (UHRF)
• UKST 6dF - Galaxy survey multi-object
  spectrograph
• ALSO OZPOZ for VLT, Echidna for Subaru

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Isaac Newton Group

• The ING is located at the Roque de Los Muchachos
  Observatory, La Palma, Spain, and it consists of
  two telescopes operating in the optical and
  near-infrared parts of the spectrum
• William Herschel Telescope (WHT) (4.2 metre
  diameter)
• Isaac Newton Telescope (INT) (2.5 metre diameter)
  
• Jacobus Kapteyn Telescope (JKT) (1.0 metre
  diameter)
• Operated on behalf of the Science and Technology
  Facilities Council (STFC) of the United Kingdom,
  the Nederlandse Organisatie voor Wetenschappelijk
  Onderzoek (NWO) of the Netherlands, and the
  Instituto de Astrofísica de Canarias (IAC) in
  Spain.

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WHT instrumentation

• Spectroscopy
• ISIS Medium-resolution (8 - 120 A/mm)
• AF2/WYFFOS Multi-object spectrograph, fed by up
  to 120 2.7" fibres from AUTOFIB2 at prime focus
  (40' field).
• INTEGRAL/WYFFOS Integral Field Unit
• LIRIS near-IR spectrograph
• Future HARPS North
• Adaptive Optics
• NAOMI
• OASIS optical IFU spectrograph
• OSCA coronograph
• INGRID IR camera.
• Rockwell 1k x 1k device.
• GLAS - laser beacon.

• Imaging
• PFIP- Prime focus
• Auxiliary port
• Private instrumentsSauron, ULTRACAM, PNS, SCAM

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INT instrumentation

• INT 2.5m
• Wide Field Prime Focus Camera
• (4 EEV 2048x4100 CCDs)
• IDS Cassegrain Intermediate Dispersion
  Spectrograph

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UKIRT

• The UK InfraRed Telescope (UKIRT) on the summit
  of Mauna Kea, Hawaii, is a 3.8 m diameter
  near-IR optimised telescope.
• It supports a range of instruments providing
  spectrometric, photometric and imaging
  capabilities.
• UKIRT is owned and operated by STFC through the
  Joint Astronomy Centre, Hawaii.

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UKIRT Instrumentation

• WFCAM Wide field 0.8-2.5 micron camera covering
  a 0.75 square degree tile in 4 pointings.
• 4 x 2048x2048 HgCdTe Hawaii-II arrays

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Telescope Parameters

• D diameter of entrance pupil
• determines light collecting power
• also limits angular resolution to 1.2?/D
  (radians)
• 1 arcsecond 1 1/206265 radians
• For a 4.2m telescope at 500nm, resolution should
  be 0.03
• in practice angular resolution on a good
  ground-based site is seldom better than 0.5 -
  mostly due to atmospheric turbulence.

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Diffraction-limited imaging(only in space or
with Adaptive Optics)
J1(2m)/m J1(2m)2/m2
Intensity
m1.916,?1.22?/D
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Telescope Parameters

• f focal length
• angular separation of 2 objects ? (radians)
  d/f
• image scale, S (in mm/arcsec) f(mm)/206265
• if f 10m, S 48?m/arcsec, typical for prime
  focus of modern 4m-class telescope.

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Telescope Parameters

• F-number or speed
• F-Numberspeedfocal ratiof/D
• Most telescopes have several foci with different
  focal ratios and re-imaging optics frequently
  change it within instruments
• Field of view
• angular area of sky which can be usefully imaged
  without excessive vignetting.

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Telescope Types optical categories

• Refractors use lens as main optical element
• e.g., Yerkes 40inch, focal length 19.4m
• larger lenses not practical
• lenses sag under their own weight
• difficult to keep refractive index constant over
  large piece of glass
• Reflectors use a primary mirror
• single mirrors up to 8m diameter have been built
  (e.g., Gemini)
• segmented mirrors up to 10m (e.g., Keck)
• modern primary mirrors can be fast ( f/3)
• to reduce size of support structure and dome

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Telescope mounts Equatorial

• RA Right Ascension, Dec Declination
• Advantages
• Only RA must be driven at a constant rate to
  track
• Star field does not rotate with time
• Disadvantages
• large, bulky, expensive

INT,La Palma
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Telescope mountsAlt-azimuth

• AltAltitude, AzAzimuth
• Disadvantages field rotation, 3 axes require
  computer control, zenith blind spot.
• Advantagessmaller, cheaper

WHT,La Palma
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Telescope Constructionthe Serrurier truss

• Preferred design for telescope tubes
• Gravitational flexure of mirror cell and top-end
  end ring are parallel and equal for all
  orientations.
• therefore optical alignment is maintained

WHT,La Palma
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Telescope Foci Prime Focus
AutoFib-2 Prime Focus Fibre Robot. Built
Durham AIG WHT,La Palma

• Focus formed by primary mirror alone
• Used for direct imaging and wide-field
  multi-object spectroscopy
• angular field of view can be up to 2 degrees
  diameter
• Image is only aberration-free for a parabola and
  only on-axis
• need a prime focus corrector to get a usable
  large field

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Telescope Foci Cassegrain Focus

• Classical Cassegrain
• paraboloidal primary and convex hyperboloidal
  secondary. WHT f/11
• mainly used for spectroscopy and polarimetry
• modest field of view (10-20 arcminutes)

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Telescope foci Coudé focus

• A stationary focus for equatorial telescopes
• Used for very high resolution (Echelle)
  spectrographs bulky, heavy instruments
• The beam must be folded through the declination
  and RA axes.
• This needs several flat mirrors and a very slow
  beam ( f/50).
• Field of view 1-2

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Telescope foci Nasmyth focus

• Gravity-stable focus on an alt-azimuth telescope
• rotates with azimuth
• a flat tertiary mirror folds light away from
  Cassegrain and through the altitude axis.
• used for heavy spectrographs
• also used for sensitive instruments
• adaptive optics

WHT f/11 Cass/Nasmyth
Tertiary flat
Nasmyth platform
Nasmyth platform
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Ritchey-Chrétien Telescopes

• Both primary and secondary mirrors are
  hyperboloids
• corrects spherical aberration and coma
• introduces large field curvature
• more easily corrected so fields are in fact large

Gemini-North, May 27, 1998
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Schmidt Telescopes

• Spherical mirror with aspheric corrector
• excellent field of view (gt 6 degrees)
• survey work
• curved focal plane
• UK Schmidt 1.2m aperture.

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Current/new generation of large telescopes

• 3 primary mirror technologies
• segmented
• lightweighted borosilicate honeycomb
• meniscus with active support

• Keck 2 telescopes, 10m segmented primary
• one working
• ESO VLT 4x 8m meniscus primaries
• LBT 2x 8.4m honeycomb primaries in binocular
  configuration with with 14.4m centre-centre
  spacing
• MMT 6.5m honeycomb primary
• Magellan 2x 6.5m honeycomb primary
• Hobby-Eberly 11m spherical segmented
• Subaru 8.3m meniscus
• Gemini 2x 8.1m meniscus (Hawaii and Chile)

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Gemini

• 2x8m
• US176M, funded by Argentina/Australia/Brazil/Ca
  nada/Chile/UK/USA
• Scientific requirements
• image quality lt0.1 arcsec
• Emissivity lt4 (2 goal)
• 8.1m ULE meniscus primary
• lightweight secondary with fast tip-tilt
• f/16 Cassegrain focus
• Active mirror support actuators
• 120 axial, 72 lateral
• Raised Alt-Az mount
• thermal control
• mirror 0.2,-0.6 ambient

Gemini-NorthMauna Kea, Hawaii 1999
Gemini-SouthCerro-Pachon, Chile 2000
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Gemini Instrumentation

• Gemini South
• T-ReCS (mid-IR imager/spectrograph)
• GMOS (optical multi-object spectrometer and
  imager)
• Phoenix (near-IR spectrograph)
• NICI near-IR coronograph
• Flamingos 2 near IR MOS
• GSAO-I near IR imager
• MCAO/Canopus !!!
• GPI (Gemini Planet Imager)

• Gemini North
• NIRI (near-IR imager)
• Michelle (mid-IR imager/spectrometer)
• GMOS (optical multi-object spectrograph and
  imager)
• NIFS (near-IR IFU, destroyed by bush fire
  18/01/03) rebuilt!)
• Altair/LGS laser guide star
• GNIRS near-IR spectrograph
• Partially destroyed by overheating 2007 under
  rebuild!

- Adaptive Optics (AO) instrumentation
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ESO VLT

• The Paranal Observatory comprises four 8 meter
  Unit Telescopes, working separately
• or at a combined interferometric focus with
  three 1.8m. diameter "outriggers" for improved
  interferometry.
• Also a 2.5 meter diameter telescope, the VST,
  will provide the OmegaCAM wide-field optical
  imaging capability.
• Also the UK 4 m diameter VISTA telescope will
  bring a very large IR-Optical wide-field
  facility.

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ESO VLT
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VLT instrumentation
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VLT instruments

• CRIRES cryogenic high-resolution IR spectrograph
  
• Resolution gt 100,000
• 1 5 microns
• 0.2 arcsec slit
• Adaptive optics

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VLT instruments

• ISAAC IR spectrometer/ camera.
• 1-2.5 µm imaging over a 2.5 arcmin x 2.5 arcmin
  field.
• 1-2.5 µm imaging polarimetry over 2.5 x 2.5
  arcmin
• 1-2.5 µm long slit low (Rs 500) and medium
  resolution (Rs 3000) spectroscopy
• 2.5-5 µm imaging over a 1.25 x 1.25 arcmin field.
  
• 2.5-5 µm long slit low (Rs 500) and medium
  resolution (Rs 3000) spectroscopy

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VLT Instruments

• FLAMES Fibre Large Array Multi Element
  Spectrograph
• 130 objects with sky on Giraffe Optical
  Spectrograph
• 8 object feed to UVES
• IFU

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VLT instrumentation

• FORS FOcal Reducer/low dispersion Spectrograph
• FORS1 imaging and long-slit / multi-object
  spectroscopy and spectopolarimetry
• FORS2 as above plus Echelle and high
  time-resolution modes

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VLT instrumentation

• VISIR mid infrared imager spectrograph
• diffraction limited imaging with variable
  magnification utilizing broad and narrow-band
  filters up to a maximum field of 80x80 arcsec ²
  between 8 - 13 µm and 16.5 - 24.0µm
• long-slit spectroscopy between 7.9 - 14 µm with R
  250 and R gt 30,000

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VLT Instrumentation

• VIMOS VIsible MultiObject Spectrograph
• Field of view 4 x 7' x 8' with 0.205"/pixel
  sampling
• Wavelength range 0.37 - 1.0 µm
• Spectral resolution for 1 arcsec slit 200
  (LR), 600 (MR), and 2000 (HR)
• 150 slits _at_ R 2000, 750 slits _at_ R 200
• Integral field Unit providing up to 54" x 54"
  field of view

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VLT instrumentation

• SINFONI - SINgle Far Object Near-ir Investigation
• integral field spectroscopy with 32 x 32 spatial
  pixels
• multiplied by 1024 spectral pixels
• spatial sampling variable from 0.25 arcsec to
  0.025 arcsec.
• 1.0 - 2.5 µm range
• spectral resolution from 1000 to 4,500
• Adaptive Optics sodium laser guide star

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VLT instrumentation

• UVES UV-Visual Echelle Spectrograph
• two-arm cross-dispersed echelle spectrograph
  covering the wavelength range 300 - 500 nm (blue)
  and 420 - 1100 nm (red)
• with the possibility to use dichroics.
• The spectral resolution for a 1 arcsec slit is
  about 40,000.
• The maximum resolution that can be attained with
  still adequate sampling, using a narrow slit, is
  about 110,000 in the red and 80,000 in the blue.

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VLT instrumentation

• CONICA Near-Infrared Camera
• 1-2.5 µm
• image scales13.25, 27.0, 54.3 mas/pixel
• NAOS Nasmyth Adaptive Optics System
• Near-IR AO system with visible or near-IR Natural
  Guide Stars

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VISTA

• NEW Visible Infrared Survey Telescope for
  Astronomy
• 75 of time on long-term targeted surveys
• 4m telescope
• IR camera 1 square degree field of view,
• zJHK, 0.34 arcsec pixels
• Paranal (VLT site)