376 research outputs found
Optimization of exposure time division for wide field observations
The optical observations of wide fields of view encounter the problem of
selection of best exposure time. As there are usually plenty of objects
observed simultaneously, the quality of photometry of the brightest ones is
always better than of the dimmer ones. Frequently all of them are equally
interesting for the astronomers and thus it is desired to have all of them
measured with the highest possible accuracy.
In this paper we present a novel optimization algorithm dedicated for the
division of exposure time into sub-exposures, which allows to perform
photometry with more balanced noise budget. Thanks to the proposed technique,
the photometric precision of dimmer objects is increased at the expense of the
measurement fidelity of the brightest ones. We tested the method on real
observations using two telescope setups demonstrating its usefulness and good
agreement with the theoretical expectations. The main application of our
approach is a wide range of sky surveys, including the ones performed by the
space telescopes. The method can be applied for planning virtually any
photometric observations, in which the objects of interest show a wide range of
magnitudes.Comment: 18 pages, 5 figure
Bad pixel modified interpolation for astronomical images
We present a new method of interpolation for the pixel brightness estimation
in astronomical images. Our new method is simple and easily implementable. We
show the comparison of this method with the widely used linear interpolation
and other interpolation algorithms using one thousand astronomical images
obtained from the Sloan Digital Sky Survey. The comparison shows that our
method improves bad pixels brightness estimation with four times lower mean
error than the presently most popular linear interpolation and has a better
performance than any other examined method. The presented idea is flexible and
can be also applied to presently used and future interpolation methods. The
proposed method is especially useful for large sky surveys image reduction but
can be also applied to single image correction.Comment: 16 pages, 10 figures. Printed in PASP, September 201
Beyond the current noise limit in imaging through turbulent medium
Shift-and-add is an approach employed to mitigate the phenomenon of
resolution degradation in images acquired through a turbulent medium. Using
this technique, a large number of consecutive short exposures is registered
below the coherence time of the atmosphere or other blurring medium. The
acquired images are shifted to the position of the brightest speckle and
stacked together to obtain high-resolution and high signal-to-noise frame. In
this paper we present a highly efficient method for determination of frames
shifts, even if in a single frame the object cannot be distinguished from the
background noise. The technique utilizes our custom genetic algorithm, which
iteratively evolves a set of image shifts. We used the maximal energy of
stacked images as an objective function for shifts estimation and validate the
efficiency of the method on simulated and real images of simple and complex
sources. Obtained results confirmed, that our proposed method allows for the
recovery of spatial distribution of objects even only 2% brighter than their
background. The presented approach extends significantly current limits of
image reconstruction with the use of shift-and-add method. The applications of
our algorithm include both the optical and the infrared imaging. Our method may
be also employed as a digital image stabilizer in extremely low light level
conditions in professional and consumer applications.Comment: 8 pages, 4 figure
Quantum Telescopes: feasibility and constrains
Quantum Telescope is a recent idea aimed at beating the diffraction limit of
spaceborne telescopes and possibly also other distant target imaging systems.
There is no agreement yet on the best setup of such devices, but some
configurations have been already proposed. In this Letter we characterize the
predicted performance of Quantum Telescopes and their possible limitations. Our
extensive simulations confirm that the presented model of such instruments is
feasible and the device can provide considerable gains in the angular
resolution of imaging in the UV, optical and infrared bands. We argue that it
is generally possible to construct and manufacture such instruments using the
latest or soon to be available technology. We refer to the latest literature to
discuss the feasibility of the proposed QT system design.Comment: Optics Letters - published after major revisio
Integrable System Constructed out of Two Interacting Superconformal Fields
We describe how it is possible to introduce the interaction between
superconformal fields of the same conformal dimensions. In the classical case
such construction can be used to the construction of the Hirota - Satsuma
equation. We construct supersymmetric Poisson tensor for such fields, which
generates a new class of Hamiltonin systems. We found Lax representation for
one of equation in this class by supersymmetrization Lax operator responsible
for Hirota - Satsuma equation. Interestingly our supersymmetric equation is not
reducible to classical Hirota - Satsuma equation. We show that our generalized
system is reduced to the one of the supersymmetric KDV equation (a=4) but in
this limit integrals of motion are not reduced to integrals of motion of the
supersymmetric KdV equation.Comment: 15 pages,late
Zero Curvature Formalism for Supersymmetric Integrable Hierarchies in Superspace
We generalize the Drinfeld-Sokolov formalism of bosonic integrable
hierarchies to superspace, in a way which systematically leads to the zero
curvature formulation for the supersymmetric integrable systems starting from
the Lax equation in superspace. We use the method of symmetric space as well as
the non-Abelian gauge technique to obtain the supersymmetric integrable
hierarchies of the AKNS type from the zero curvature condition in superspace
with the graded algebras, sl(n+1,n), providing the Hermitian symmetric space
structure.Comment: LaTeX, 9 pg
Supersymmetric Non-local Gas Equation
In this paper we study systematically the question of supersymmetrization of
the non-local gas equation. We obtain both the N=1 and the N=2 supersymmetric
generalizations of the system which are integrable. We show that both the
systems are bi-Hamiltonian. While the N=1 supersymmetrization allows the
hierarchy of equations to be extended to negative orders (local equations), we
argue that this is not the case for the N=2 supersymmetrization. In the bosonic
limit, however, the N=2 system of equations lead to a new coupled integrable
system of equations.Comment: RevTex, 7page
Differential-Algebraic Integrability Analysis of the Generalized Riemann Type and Korteweg-de Vries Hydrodynamical Equations
A differential-algebraic approach to studying the Lax type integrability of
the generalized Riemann type hydrodynamic equations at N = 3; 4 is devised. The
approach is also applied to studying the Lax type integrability of the well
known Korteweg-de Vries dynamical system.Comment: 11 page
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