Astronomy and Astrophysics – Astrophysics – Instrumentation and Methods for Astrophysics
Scientific paper
2011-09-12
Astronomy and Astrophysics
Astrophysics
Instrumentation and Methods for Astrophysics
14 pages, 16 figures, accepted by A&A. Version V2 revised for language editing
Scientific paper
10.1051/0004-6361/201015702
Stray light caused by scattering on optical surfaces and in the Earth's atmosphere degrades the spatial resolution of observations. We study the contribution of stray light to the two channels of POLIS. We test the performance of different methods of stray-light correction and spatial deconvolution to improve the spatial resolution post-facto. We model the stray light as having two components: a spectrally dispersed component and a component of parasitic light caused by scattering inside the spectrograph. We use several measurements to estimate the two contributions: observations with a (partly) blocked FOV, a convolution of the FTS spectral atlas, imaging in the pupil plane, umbral profiles, and spurious polarization signal in telluric lines. The measurements allow us to estimate the spatial PSF of POLIS and the main spectrograph of the German VTT. We use the PSF for a deconvolution of both spectropolarimetric data and investigate the effect on the spectra. The parasitic contribution can be directly and accurately determined for POLIS, amounting to about 5%. We estimate a lower limit of about 10% across the full FOV for the dispersed stray light. In quiet Sun regions, the stray-light level from the close surroundings (d< 2") of a given spatial point is about 20%. The stray light reduces to below 2% at a distance of 20" from a lit area for both POLIS and the main spectrograph. A two-component model of the stray-light contributions seems to be sufficient for a basic correction of observed spectra. The instrumental PSF obtained can be used to model the off-limb stray light, to determine the stray-light contamination accurately for observation targets with large spatial intensity gradients such as sunspots, and also allows one to improve the spatial resolution of observations post-facto.
Beck Ch.
Fabbian Damian
Rezaei Rashid
No associations
LandOfFree
Stray-light contamination and spatial deconvolution of slit-spectrograph observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Stray-light contamination and spatial deconvolution of slit-spectrograph observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stray-light contamination and spatial deconvolution of slit-spectrograph observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-59744