The Thresher: Lucky imaging without the waste. Issue 4 (17th February 2022)

• Record Type: Journal Article
• Authors: Hitchcock, J A; Bramich, D M; Foreman-Mackey, D; Hogg, David W; Hundertmark, M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 4(2022)
• Page Start: 5372
• Page End: 5384
• Publication Date: 2022-02-17
• Subjects: instrumentation: detectors -- methods: data analysis -- techniques: image processing; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac427
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: In traditional lucky imaging (TLI), many consecutive images of the same scene are taken with a high frame-rate camera, and all but the sharpest images are discarded before constructing the final shift-and-add image. Here, we present an alternative image analysis pipeline – The Thresher – for these kinds of data, based on online multi-frame blind deconvolution. It makes use of all available data to obtain the best estimate of the astronomical scene in the context of reasonable computational limits; it does not require prior estimates of the point-spread functions in the images, or knowledge of point sources in the scene that could provide such estimates. Most importantly, the scene it aims to return is the optimum of a justified scalar objective based on the likelihood function. Because it uses the full set of images in the stack, The Thresher outperforms TLI in signal-to-noise ratio; as it accounts for the individual-frame PSFs, it does this without loss of angular resolution. We demonstrate the effectiveness of our algorithm on both simulated data and real Electron-Multiplying CCD images obtained at the Danish 1.54-m telescope (hosted by ESO, La Silla). We also explore the current limitations of the algorithm, and find that for the choice of image model presented here, non-linearities in flux are introduced into the returned scene. Ongoing development of the software can be viewed at https://github.com/jah1994/TheThresher .