Lucky imaging: high angular resolution imaging in the visible from the ground

Law, Nicholas M.; Mackay, Craig D.; Baldwin, John E.

doi:10.1051/0004-6361:20053695

Cited by 231 publications

(203 citation statements)

References 11 publications

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“…From the ground, adaptive optics is one answer to the first requirement. Other techniques exist such as speckle imaging [3], lucky imaging [4], sparse aperture masking [5], interferometry [6], but AO-assisted imaging is currently the only option to reach Fig. 2 Typical contrast obtained on sky in the H band from the first generation of AO systems (NaCo, NIRC2, NICI, HiCIAO, green curve), the second generation of extreme AO system (SPHERE/GPI, red curve), compared to the space-based instrument HST/NICMOS (blue curve).…”

Section: Requirementsmentioning

confidence: 99%

Adaptive Optics in High-Contrast Imaging

Milli¹,

Mawet²,

Mouillet³

et al. 2016

Astronomy at High Angular Resolution

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The development of adaptive optics (AO) played a major role in modern astronomy over the last three decades. By compensating for the atmospheric turbulence, these systems enable to reach the diffraction limit on large telescopes. In this review, we will focus on high contrast applications of adaptive optics, namely, imaging the close vicinity of bright stellar objects and revealing regions otherwise hidden within the turbulent halo of the atmosphere to look for objects with a contrast ratio lower than 10 −4 with respect to the central star. Such high-contrast AO-corrected observations have led to fundamental results in our current understanding of planetary formation and evolution as well as stellar evolution. AO systems equipped three generations of instruments, from the first pioneering experiments in the nineties, to the first wave of instruments on 8m-class telescopes in the years 2000, and finally to the extreme AO systems that have recently started operations. Along with highcontrast techniques, AO enables to reveal the circumstellar environment: massive protoplanetary disks featuring spiral arms, gaps or other asymetries hinting at ongoing planet formation, young giant planets shining in thermal emission, or tenuous debris disks and micron-sized dust leftover from collisions in massive asteroid-belt analogs. After introducing the science case and technical requirements, we will review the architecture of standard and extreme AO systems, before presenting a few selected science highlights obtained with recent AO instruments.

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Section: Requirementsmentioning

confidence: 99%

Adaptive Optics in High-Contrast Imaging

Milli¹,

Mawet²,

Mouillet³

et al. 2016

Astronomy at High Angular Resolution

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show abstract

“…This method is different from the more common method of registering the frames based on one or more centroids (Mackay et al 2004;Law et al 2006). Given a set of bias-and flat field-corrected images {I i (x, y)}, as described earlier, we will generate a reference image R by taking the average…”

Section: Correcting Tip and Tiltmentioning

confidence: 99%

“…Because the analogy between the photomultiplier and the EMCCD, much of the statistics developed for the photomultiplier can be reused when dealing with an EMCCD. The possibility of doing high frame rate imaging, like lucky imaging, has been explored in numerous other articles and theses; see for instance Mackay et al (2004); Law et al (2006).…”

Section: Introductionmentioning

confidence: 99%

High frame rate imaging based photometry

Harpsøe

Jørgensen

Andersen

et al. 2012

A&A

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Context. The EMCCD is a type of CCD that delivers fast readout times and negligible readout noise, making it an ideal detector for high frame rate applications which improve resolution, like lucky imaging or shift-and-add. This improvement in resolution can potentially improve the photometry of faint stars in extremely crowded fields significantly by alleviating crowding. Alleviating crowding is a prerequisite for observing gravitational microlensing in main sequence stars towards the galactic bulge. However, the photometric stability of this device has not been assessed. The EMCCD has sources of noise not found in conventional CCDs, and new methods for handling these must be developed. Aims. We aim to investigate how the normal photometric reduction steps from conventional CCDs should be adjusted to be applicable to EMCCD data. One complication is that a bias frame cannot be obtained conventionally, as the output from an EMCCD is not normally distributed. Also, the readout process generates spurious charges in any CCD, but in EMCCD data, these charges are visible as opposed to the conventional CCD. Furthermore we aim to eliminate the photon waste associated with lucky imaging by combining this method with shift-and-add. Methods. A simple probabilistic model for the dark output of an EMCCD is developed. Fitting this model with the expectationmaximization algorithm allows us to estimate the bias, readout noise, amplification, and spurious charge rate per pixel and thus correct for these phenomena. To investigate the stability of the photometry, corrected frames of a crowded field are reduced with a point spread function (PSF) fitting photometry package, where a lucky image is used as a reference. Results. We find that it is possible to develop an algorithm that elegantly reduces EMCCD data and produces stable photometry at the 1% level in an extremely crowded field.

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“…This in turn has led to a new method: lucky imaging, which can to some degree overcome atmospherically-induced resolution limitations of ground-based telescopes (Law et al 2006;Oscoz et al 2008;Hormuth et al 2008). The lucky imaging idea is based on the work of Fried (1978) (who computed the probability of getting a lucky frame, i.e., an image recorded at a time instant of exceptionally good seeing).…”

Section: Extended Labeyrie's Idea Bymentioning

confidence: 99%

Online multi-frame blind deconvolution with super-resolution and saturation correction

Hirsch

Harmeling

Sra

et al. 2011

A&A

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Astronomical images taken by ground-based telescopes suffer degradation due to atmospheric turbulence. This degradation can be tackled by costly hardware-based approaches such as adaptive optics, or by sophisticated software-based methods such as lucky imaging, speckle imaging, or multi-frame deconvolution. Software-based methods process a sequence of images to reconstruct a deblurred high-quality image. However, existing approaches are limited in one or several aspects: (i) they process all images in batch mode, which for thousands of images is prohibitive; (ii) they do not reconstruct a super-resolved image, even though an image sequence often contains enough information; (iii) they are unable to deal with saturated pixels; and (iv) they are usually non-blind, i.e., they assume the blur kernels to be known. In this paper we present a new method for multi-frame deconvolution called online blind deconvolution (OBD) that overcomes all these limitations simultaneously. Encouraging results on simulated and real astronomical images demonstrate that OBD yields deblurred images of comparable and often better quality than existing approaches.

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Lucky imaging: high angular resolution imaging in the visible from the ground

Cited by 231 publications

References 11 publications

Adaptive Optics in High-Contrast Imaging

Adaptive Optics in High-Contrast Imaging

High frame rate imaging based photometry

Online multi-frame blind deconvolution with super-resolution and saturation correction

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