Experimental evaluation of computerised tomography point spread function variability within the field of view: Parametric models

2004 ◽  
Vol 42 (5) ◽  
pp. 591-597
Author(s):  
S. Doré ◽  
R. E. Kearney
Keyword(s):  
Point Spread Function ◽  
Experimental Evaluation ◽  
Parametric Models ◽  
Field Of View ◽  
Computerised Tomography ◽  
Point Spread ◽  
Spread Function

Improving position accuracy for telescopes with small aperture and wide field of view utilizing point spread function modelling

2020 ◽  
Vol 497 (3) ◽  
pp. 4000-4008
Author(s):  
Rongyu Sun ◽  
Shengxian Yu ◽  
Peng Jia ◽  
Changyin Zhao
Keyword(s):  
Point Spread Function ◽  
Large Scale ◽  
Field Of View ◽  
Wide Field ◽  
Position Measurement ◽  
Small Aperture ◽  
Position Accuracy ◽  
Point Spread ◽  
Wide Field Of View ◽  
Spread Function

ABSTRACT Telescopes with a small aperture and a wide field of view are widely used and play a significant role in large-scale state-of-the-art sky survey applications, such as transient detection and near-Earth object observations. However, owing to the specific defects caused by optical aberrations, the image quality and efficiency of source detection are affected. To achieve high-accuracy position measurements, an innovative technique is proposed. First, a large number of raw images are analysed using principal component analysis. Then, the effective point spread function is reconstructed, which reflects the state of the telescope and reveals the characteristics of the imaging process. Finally, based on the point spread function model, the centroids of star images are estimated iteratively. To test the efficiency and reliability of our algorithm, a large number of simulated images are produced, and a telescope with small aperture and wide field of view is utilized to acquire the raw images. The position measurement of sources is performed using our novel method and two other common methods on these data. Based on a comparison of the results, the improvement is investigated, and it is demonstrated that our proposed technique outperforms the others on position accuracy. We explore the limitations and potential gains that may be achieved by applying this technique to custom systems designed specifically for wide-field astronomical applications.

scholarly journals Spatial likelihood analysis for MAGIC telescope data

2018 ◽  
Vol 619 ◽  
pp. A7 ◽  
Author(s):  
I. Vovk ◽  
M. Strzys ◽  
C. Fruck
Keyword(s):  
Point Spread Function ◽  
Field Of View ◽  
Source Analysis ◽  
Source Information ◽  
Cherenkov Telescopes ◽  
Point Spread ◽  
Upper Limits ◽  
Spread Function ◽  
Source Models ◽  
Extended Sources

Context. The increase in sensitivity of Imaging Atmospheric Cherenkov Telescopes (IACTs) has lead to numerous detections of extended γ-ray sources at TeV energies, sometimes of sizes comparable to the instrument’s field of view. This creates a demand for advanced and flexible data analysis methods that are able to extract source information using the photon counts in the entire field of view. Aims. We present a new software package, “SkyPrism”, aimed at performing 2D (3D if energy is considered) fits of IACT data that possibly contain multiple and extended sources. The fits are based on sky images binned in energy. Although the development of this package was focused on the analysis of data collected with the MAGIC telescopes, it can further be adapted to other instruments, such as the future Cherenkov Telescope Array. Methods. We have developed a set of tools that in addition to sky images (count maps) compute the instrument response functions of MAGIC (effective exposure throughout the field of view, point spread function, energy resolution, and background shape) based on the input data, Monte Carlo simulations, and the pointing track of the telescopes. With this information, the package can perform a simultaneous maximum likelihood fit of source models of arbitrary morphology to the sky images providing energy spectra, detection significances, and upper limits. Results. We demonstrate that the SkyPrism tool accurately reconstructs the MAGIC point spread function, on- and off-axis performance as well as the underlying background. We further show that for a point source analysis with the MAGIC default observational settings, SkyPrism gives results compatible with those of the standard tools while being more flexible and widely applicable.

scholarly journals Dark Energy Survey year 3 results: point spread function modelling

2020 ◽  
Vol 501 (1) ◽  
pp. 1282-1299
Author(s):  
M Jarvis ◽  
G M Bernstein ◽  
A Amon ◽  
C Davis ◽  
P F Léget ◽  
...  
Keyword(s):  
Dark Energy ◽  
Point Spread Function ◽  
Systematic Errors ◽  
Field Of View ◽  
Dark Energy Survey ◽  
Point Spread ◽  
Spread Function ◽  
Function Modelling ◽  
Astronomical Images ◽  
Energy Survey

ABSTRACT We introduce a new software package for modelling the point spread function (PSF) of astronomical images, called piff (PSFs In the Full FOV), which we apply to the first three years (known as Y3) of the Dark Energy Survey (DES) data. We describe the relevant details about the algorithms used by piff to model the PSF, including how the PSF model varies across the field of view (FOV). Diagnostic results show that the systematic errors from the PSF modelling are very small over the range of scales that are important for the DES Y3 weak lensing analysis. In particular, the systematic errors from the PSF modelling are significantly smaller than the corresponding results from the DES year one (Y1) analysis. We also briefly describe some planned improvements to piff that we expect to further reduce the modelling errors in future analyses.

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