Issue |
A&A
Volume 480, Number 2, March III 2008
|
|
---|---|---|
Page(s) | 589 - 597 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20079214 | |
Published online | 09 January 2008 |
The point spread function in Lucky Imaging and variations in seeing on short timescales
1
Cavendish Laboratory, Madingley Rd, Cambridge CB3 0HE, UK e-mail: [jeb;pjw]@mrao.cam.ac.uk
2
Institute of Astronomy, Madingley Rd, Cambridge CB3 0HE, UK e-mail: cdm@ast.cam.ac.uk
Received:
7
December
2007
Accepted:
22
December
2007
Aims.We investigate the properties of astronomical images made by combining the best images selected from a sequence of short-exposure frames (Lucky Imaging); we assess the match between modelling and observation and discover what variations in seeing occur on very short timescales.
Methods.Numerical simulations of a random phase-changing screen passing across a telescope aperture with ideal optics are used to determine the expected point spread function and isoplanatic properties for a range of seeing conditions for comparison with observations.
Results.All the model images comprise a diffraction-limited core with Strehl ratios from 0.05–0.5 and an underlying broad disk. The isoplanatic patch sizes are large and coherence times long. The observations are a close match to the models in most respects. Large variations in seeing occur on temporal scales as short as 0.2 s and spatial scales as small as 1 m.
Key words: atmospheric effects / techniques: high angular resolution
© ESO, 2008
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