scholarly journals Advanced Processing of Images Obtained from Wide-field Astronomical Optical Systems

10.14311/1334 ◽  
2011 ◽  
Vol 51 (1) ◽  
Author(s):  
M. Řeřábek ◽  
P. Páta
Keyword(s):  
Image Data ◽  
Optical Systems ◽  
General View ◽  
Wide Field ◽  
Optical Aberrations ◽  
Transfer Characteristics ◽  
Astronomical Image ◽  
Wide Range ◽  
Spread Function ◽  
Space Variant

The principal aim of this paper is to present a general view of the special optical systems used for acquiring astronomical image data, commonly referred to as WFC or UWFC (Ultra Wide Field Camera), and of their transfer characteristics. UWFC image data analysis is very difficult in general, not only because the systems have so-called space variant (SV) properties. Images obtained from UWFC systems are usually incorrectly presented due to a wide range of optical aberrations and distortions. The influence of the optical aberrations increases towards the margins of the field of view. These aberrations distort the point spread function of the optical system and rapidly cut the accuracy of the measurements. This paper deals with simulation and modelling of the UWFC optical systems used in astronomy and their transfer characteristics.

scholarly journals Space Variant PSF – Deconvolution of Wide-Field Astronomical Images

10.14311/1023 ◽  
2008 ◽  
Vol 48 (3) ◽  
Author(s):  
M. Řeřábek
Keyword(s):  
Optical System ◽  
Imaging System ◽  
Real Data ◽  
Wavefront Aberration ◽  
Wide Field ◽  
Optical Aberrations ◽  
Optical Aberration ◽  
Transfer Characteristics ◽  
Astronomical Images ◽  
Space Variant

The properties of UWFC (Ultra Wide-Field Camera) astronomical systems along with specific visual data in astronomical images contribute to a comprehensive evaluation of the acquired image data. These systems contain many different kinds of optical aberrations which have a negatively effect on image quality and imaging system transfer characteristics, and reduce the precision of astronomical measurement. It is very important to figure two main questions out. At first: In which astrometric depend on optical aberrations? And at second: How optical aberrations affect the transfer characteristics of the whole optical system. If we define the PSF (Point Spread Function) [2] of an optical system, we can use some suitable methods for restoring the original image. Optical aberration models for LSI/LSV (Linear Space Invariant/Variant) [2] systems are presented in this paper. These models are based on Seidel and Zernike approximating polynomials [1]. Optical aberration models serve as suitable tool for estimating and fitting the wavefront aberration of a real optical system. Real data from the BOOTES (Burst Observer and Optical Transient Exploring System) experiment is used for our simulations. Problems related to UWFC imaging systems, especially a restoration method in the presence of space variant PSF are described in this paper. A model of the space variant imaging system and partially of the space variant optical system has been implemented in MATLAB. The “brute force” method has been used for restoration of the testing images. The results of different deconvolution algorithms are demonstrated in this paper. This approach could help to improve the precision of astronomic measurements. 

Space variant point spread function modeling for astronomical image data processing

2007 ◽  
Author(s):  
Martin Řeřábek ◽  
Petr Páta ◽  
Karel Fliegel ◽  
Jan Švihlik ◽  
Pavel Koten
Keyword(s):  
Data Processing ◽  
Point Spread Function ◽  
Image Data ◽  
Astronomical Image ◽  
Point Spread ◽  
Spread Function ◽  
Space Variant

scholarly journals HST Image Restoration: Current Capabilities and Future Prospects

1994 ◽  
Vol 158 ◽  
pp. 61-69 ◽  
Author(s):  
Robert J. Hanisch ◽  
Richard L. White
Keyword(s):  
Image Restoration ◽  
Dynamic Range ◽  
Hubble Space Telescope ◽  
Spherical Aberration ◽  
Wide Field ◽  
Secondary Mirror ◽  
Faint Object ◽  
Spread Function ◽  
Restoration Algorithms ◽  
Space Variant

The spherical aberration in the primary mirror of the Hubble Space Telescope causes more than 80% of the light from a point source to be spread into a halo of radius of 2–3 arcsec. The point spread function (PSF) is both time variant (resulting from spacecraft jitter and desorption of the secondary mirror support structure) and space variant (owing to the Cassegrain repeater optics in the Wide Field / Planetary Camera). A variety of image restoration algorithms have been utilized on HST data with some success, although optimal restorations require better modeling of the PSF and the development of efficient restoration algorithms that accommodate a spacevariant PSF. The first HST servicing mission (December 1993) will deploy a corrective optics system for the Faint Object Camera and the two spectrographs and a second generation WF/PC with internal corrective optics. As simulations demonstrate, however, the restoration algorithms developed now for aberrated images will be very useful for removing the remaining diffraction features and optimizing dynamic range in post-servicing mission data.

A NOVEL ANALYTICAL SPACE-VARIANT POINT SPREAD FUNCTION MODEL FOR UNDERCORRECTED OPTICAL SYSTEMS

2000 ◽  
Vol 10 (05n06) ◽  
pp. 305-313
Author(s):  
THOMAS P. COSTELLO ◽  
WASFY B. MIKHAEL
Keyword(s):  
Point Spread Function ◽  
Diffraction Theory ◽  
Optical Systems ◽  
Optical Transfer Function ◽  
Point Spread ◽  
Proposed Model ◽  
Direct Sampling ◽  
Spread Function ◽  
Optical Transfer ◽  
Space Variant

An analytical model is developed for the space-variant (SV) point-spread-function (PSF) of an undercorrected optical system with a rectangular aperture. The model accommodates broadening and shifting of the central lobe, as well as sidelobe asymmetry of the PSF, as field angle increases. These effects are exhibited by diffraction-based PSF models. The proposed model uses eight parameters for any specific field position, compared to ~ 210 parameters required for direct sampling of an individual PSF. The model is adapted to PSFs developed from diffraction theory using an adaptive system with gradient descent parameter adjustment. Consequently, the model is useful for applying certain SV digital image restoration methods because it significantly reduces the memory required to store PSF sample functions. In addition, the model does not require samples of the PSF or a DFT operation to obtain samples of the optical transfer function (OTF). Thus, the efficiency of SV restoration methods applied in the frequency domain, such as sectioning approaches, is further improved. Data presented confirms the accuracy and the computational advantage of the model by quantifying its adaptation to a physical PSF over a range of field angles.

Processing of the astronomical image data obtained from UWFC optical systems

2008 ◽  
Author(s):  
Martin Řeřábek ◽  
Petr Páta ◽  
Pavel Koten
Keyword(s):  
Image Data ◽  
Optical Systems ◽  
Astronomical Image

scholarly journals LSST Data Management: Entering the Era of Petascale Optical Astronomy

2012 ◽  
Vol 10 (H16) ◽  
pp. 675-676 ◽  
Author(s):  
Mario Juric ◽  
Tony Tyson
Keyword(s):  
Dark Energy ◽  
Image Data ◽  
Scaling Up ◽  
Wide Field ◽  
Data Set ◽  
Full Dataset ◽  
Wide Range ◽  
Optical Astronomy ◽  
Annual Scale ◽  
Nature Quality

AbstractThe Large Synoptic Survey Telescope (LSST; Ivezic et al.2008, http://lsst.org) is a planned, large-aperture, wide-field, ground-based telescope that will survey half the sky every few nights in six optical bands from 320 to 1050 nm. It will explore a wide range of astrophysical questions, ranging from discovering killer asteroids, to examining the nature of dark energy. LSST will produce on average 15 terabytes of data per night, yielding an (uncompressed) data set of 200 petabytes at the end of its 10-year mission. Dedicated HPC facilities (with a total of 320 TFLOPS at start, scaling up to 1.7 PFLOPS by the end) will process the image data in near real time, with full-dataset reprocessing on annual scale. The nature, quality, and volume of LSST data will be unprecedented, so the data system design requires petascale storage, terascale computing, and gigascale communications.

scholarly journals The Point Spread Function Variations inside Wide-field Astonomical Images

10.14311/1696 ◽  
2013 ◽  
Vol 53 (1) ◽  
Author(s):  
Elena Anisimova ◽  
Jan Bednář ◽  
Petr Páta
Keyword(s):  
Point Spread Function ◽  
Imaging System ◽  
Wide Field ◽  
Optical Aberrations ◽  
Atmospheric Scattering ◽  
Function Fitting ◽  
Astronomical Imaging ◽  
Point Spread ◽  
Spread Function ◽  
Field Imaging

The Point Spread Function (PSF) of the astronomical imaging system is usually approximated by a Gaussian or Moffat function. For simplification, the astronomical imaging system is considered to be time and space invariant. This means that invariable PSF within an exposed image is assumed. If real wide-field imaging systems are considered, this presumption is not fulfilled. In real systems, stronger optical aberrations are expected (especially coma) at greater distances from the center of the captured image. This impacts the efficiency of stellar astrometry and photometry algorithms, so it is necessary to know the PSF variation. In this paper, we perform the first step toward assigning PSF changes: we study the dependence of the Moffat function fitting parameters (FWHM and the atmospheric scattering coefficient ) on the position of a stellar object.

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