Transcript High-Resolution Imaging in the Visible on Large Ground

High-resolution imaging in the visible
on large ground-based telescopes
The Adaptive Optics Lucky Imager
Jonathan Crass
Institute of Astronomy, University of Cambridge
Craig Mackay, Rafael Rebolo-López, David King, Victor González Escalera, Marta Puga
Antolín, Antonio Pérez Garrido, Lucas Labadie, Roberto López, Alex Oscoz, Jorge
Andrés Pérez Prieto, Luis Rodríguez-Ramos, Sergio Velasco, Isidro Villo
SPIE Astronomical Telescopes and Instrumentation
June 2014, Montreal
Outline
• Motivation and background
• The Adaptive Optics Lucky Imager
• AO and lucky imaging systems
• Optical design & systems
• On-sky results
• Future work
Motivation
How to get diffraction limited imaging in the optical?
Adaptive optics
It’s hard to do AO at optical wavelengths
Lucky imaging
Only works on telescopes up ~2.5m in diameter
Combine the two together – diffraction limited imaging in
the visible
Adaptive Optics and Lucky Imaging
HST - ACS
Lucky – 10%
Fourier – 20%
Fourier – 50%
High-Efficiency Lucky Imaging
• The sharpest images come from the smallest fraction of
images.
• Often the poorer quality images are only smeared in one
direction.
• Garrel et al (PASP, 2012) suggested making the lucky
selection in Fourier space rather than image space.
High-Efficiency Lucky Imaging
High-efficiency lucky imaging
Mackay 2013, MNRAS, 432, 702
About AOLI
• Initially for the 4.2m William Herschel Telescope
• Lucky Imaging based science instrument:
• 4 × 1024 square EMCCDs (E2V CCD201) providing 2000×2000px
imaging region
• Pixel scale of 18-55 milliarcseconds in I-band
• Field of view ranging from 37.5 to 112.5 arcseconds
• AO component:
• ALPAO 241 actuator deformable mirror (DM241-25)
• Non-linear curvature wavefront sensor
•
Comprises 2 EMCCDs
Non-linear Curvature Wavefront Sensor
• nlCWFS offers:
• High sensitivity to low and high orders
• Reconstruction with ≈100-1000 fewer photons than conventional
techniques
Talk 9148-81 – Friday 11:05am (Jonathan Crass)
The AOLI low-order non-linear curvature
wavefront sensor: laboratory and on-sky results
AOLI Optics
Wavefront sensor layout
Science Camera
Calibration System
Poster 9147-294 – Wednesday
(Marta Puga Antolín)
An atmospheric turbulence and telescope
simulator for the development of AOLI
AOLI at the WHT
The initial run had four key aims:
1. To collect data from the nlCWFS for post-processing
analysis and reconstruction.
2. To collect data using the science camera to verify its optical
quality and sensitivity.
3. To collect synchronised data between the nlCWFS and
science camera to allow comparison between reconstructed
wavefronts and the science image.
4. To collect data with the calibration system to verify its
characteristics against on-sky data.
AOLI at the WHT
AOLI at the WHT
On-sky data
On-sky data: Real-time lucky
On-sky data: Post processing
Velasco et al., 2014,
MNRAS (In Prep)
Summary & Future Work
Summary
Future Work
• The combination of AO and
lucky
imaging
allows
diffraction limited imaging in
the visible.
• Redesign
of
some
mechanisms and supports
within instrument to improve
performance.
• The AOLI science camera
data matches well with design
specification.
• Issues experienced on first
on-sky run identified and
solutions implemented or
proposed.
• Fully develop AO system to
provide diffraction limited
imaging at the WHT.
• AOLI has the potential to
feed not only an imaging
camera but also an integral
field spectrograph or other
instruments.
• Aim to revisit the WHT in
2015.