How to build an artificial star

Abstract. Introduction: There is few evidence that details the behavior of each spatiotemporal variable of the running pattern of female soccer players using different surfaces. Objective: To describe the spatiotemporal variables of the sprint pattern developed on natural and artificial turf by professional female soccer players. Methods: A cross-sectional study was conducted on nineteen (n=19) professional athletes with an average age of 22.3 years, who´s sprint spatiotemporal variables were evaluated in a natural (Bermuda 419) and artificial (Star 2) playing field through an optical measurement system (Opto Gait, Italy). The analysis of the differences of the space and time variables by turf was done with the Wilcoxon test for paired data and the differences in speed and acceleration by playing position was done using the Kruskal–Wallis test. The Spearman test was used to compare the correlation between speed, acceleration and anthropometric variables. Finally, an alpha level of 5% was considered for the whole analysis. Results: On the natural turf, the speed and cadence of the players were higher; on the artificial turf, the energy, flight time, contact phase and step angle were higher (p<0.05). On the other hand, an indirect relationship was observed between speed, contact time, percentage and fat weight (p=0.01). Conclusion: Our results suggest that the natural turf, Bermuda 419, allows for a faster sprinting patterns, characterized by lower energy use, flight time, contact phase and step angle. Resumen. Introducción: Existe poca evidencia que detalle el comportamiento de cada variable espaciotemporal del patrón de carrera de mujeres futbolistas utilizando diferentes superficies. Objetivo: describir las variables espacio temporales del patrón de carrera desarrollado en superficie natural y artificial por mujeres futbolistas profesionales. Métodos: se realizó un estudio de corte transversal en diecinueve (n=19) deportistas profesionales con un promedio de edad de 22.3 años, a quienes se les evaluaron las variables espacio temporales de la carrera en césped natural (Bermuda 419) y artificial (Star 2) a través de un sistema de medición óptico (Opto Gait). El análisis de las diferencias de las variables espacio temporales fue realizado con el test de Wilcoxon para datos pareados y las diferencias en la velocidad y aceleración fue realizados usando el test Kruskal-Wallis. El test de Spearman se usó para comparar la correlación entre las variables de velocidad, aceleración y antropométricas. Finalmente, un nivel de alpha de 5% fue considerado para el análisis total. Resultados: en la superficie natural, la velocidad y cadencia de las futbolistas fueron superiores; sobre superficie artificial, la energía, el tiempo de vuelo, la fase de contacto y el ángulo de paso fueron más altas (p<0.05). De otra parte, se observó una relación indirecta entre la velocidad, tiempo de contacto, porcentaje y peso graso (p=0.01). Conclusión: nuestros resultados sugieren que la superficie natural, Bermuda 419, permite un patrón de carrera más rápido, caracterizado por un menor uso de energía, tiempo de vuelo, fase de contacto y ángulo de paso.

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Artificial Star Test for Crowded Field CCD Photometry

Open Astronomy ◽

10.1515/astro-2017-0232 ◽

2015 ◽

Vol 24 (3) ◽

Cited By ~ 1

Author(s):

R. Stonkutė ◽

V. Vansevičius

Keyword(s):

Error Estimates ◽

Spatial Resolution ◽

New Method ◽

Ccd Photometry ◽

Artificial Star ◽

Star Test

AbstractA new method of performing an artificial star test (AST) for crowded field stellar CCD photometry is proposed. This AST method is superior in the cases when it is necessary to account for varying photometric quality across the study field, arising due to crowding variations. For this purpose, the color-magnitude diagrams (CMDs) of AST stars with statistically reliable error estimates, as well as completeness maps, can be generated at a required spatial resolution.

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Mapping the stellar age of the Milky Way bulge with the VVV

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935730 ◽

2019 ◽

Vol 629 ◽

pp. A1 ◽

Cited By ~ 10

Author(s):

F. Surot ◽

E. Valenti ◽

S. L. Hidalgo ◽

M. Zoccali ◽

O. A. Gonzalez ◽

...

Keyword(s):

Surface Brightness ◽

Main Sequence ◽

Milky Way ◽

Stellar Content ◽

Star Count ◽

Spread Function ◽

The Galaxy ◽

Photometric Measurements ◽

Artificial Star ◽

Different Levels

Context. The bulge represents the best compromise between old and massive Galactic components, and as such its study is a valuable opportunity to understand how the bulk of the Milky Way formed and evolved. In addition, being the only bulge in which we can individually resolve stars in all evolutionary sequences, the properties of its stellar content provide crucial insights into the formation of bulges. Aims. We are providing a detailed and comprehensive census of the Milky Way bulge stellar populations by producing deep and accurate photometric catalogs of the inner ∼300 deg2 of the Galaxy. Methods. We performed DAOPHOT/ALLFRAME point spread function (PSF) fitting photometry of multi-epochs J and Ks images provided by the VISTA Variables in the Vía Láctea (VVV) survey to obtain deep photometric catalogs. Artificial star experiments have been conducted on all images to properly assess the completeness and the accuracy of the photometric measurements. Results. We present a photometric database containing nearly 600 million stars across the bulge area surveyed by the VVV. Through the comparison of derived color-magnitude diagrams of selected fields representative of different levels of extinction and crowding, we show the quality, completeness and depth of the new catalogs. With the exception of the fields located along the plane, this new photometry samples stars down to ∼1–2 mag below the old main sequence turnoff with unprecedented accuracy. To demonstrate the tremendous potential inherent to this new dataset, we give a few examples of possible applications, including (i) star count studies through the dataset completeness map; (ii) surface brightness map; and (iii) cross-correlation with Gaia DR2. Conclusions. The database presented here represents an invaluable collection for the whole community, and we encourage its exploitation. The photometric catalogs including completeness information are publicly available through the ESO Science Archive as part of the MW-BULGE-PSPHOT release.

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On the nature of the diffraction figures due to the heliometer

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1910.0018 ◽

1910 ◽

Vol 83 (563) ◽

pp. 302-323 ◽

Cited By ~ 3

Keyword(s):

Spherical Aberration ◽

Position Angle ◽

Double Star ◽

Personal Equation ◽

The Subject ◽

Artificial Star ◽

The One ◽

Star Images ◽

Made In

1. In investigating the influence of personal equation in connection with double star measurements, the actual values of distance and position angle must be known, and hence the only possible method is to use an artificial star. The method adopted in the Students’ Observatory at University College, in order to obtain a known separation and direction, is to use a weak heliometer lens in front of the equatorial and a spark between cadmium electrodes some distance away. The direction of the line joining the two “star” images and the distance between them can be measured by a divided circle and micrometer screw respectively, while the intensity of the stars can be altered by using various stops. It was found that when a moderately small stop was used, the diffraction images became quite perceptible, and hence, before any further progress could be made in the determination of personal equation, it was necessary to investigate these diffraction images. 2. On consulting the literature of the subject, I found that the earliest papers dealing with the diffraction figure of the heliometer are by Bessel. He observed ( a ) that two opposite brushes of light emerged from the central disc perpendicularly to the line of separation; ( b ) that when the halves of the lens were separated, the disc was lengthened in the direction perpendicular to the line of separation; and ( c ) that the brushes of light were of equal length when the halves were united; but that, when the halves were separated, the brush of light on the same side of the image as the half-lens forming it was longer than the one on the opposite side; and he attributed the lengthening of the disc formed by the half-lens to the fact that the lens was corrected for spherical aberration for the whole lens, and not for the two halves separately.

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An artificial star source for the OAO

10.6028/nbs.rpt.8619 ◽

1964 ◽

Author(s):

D Sirota

Keyword(s):

Artificial Star

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Sirius: a prototype astronomical intensity interferometer using avalanche photodiodes in linear mode

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3584 ◽

2020 ◽

Vol 500 (4) ◽

pp. 5630-5638

Author(s):

Junghwan Oh ◽

Jan Wagner ◽

Sascha Trippe ◽

Taeseok Lee ◽

Bangwon Lee ◽

...

Keyword(s):

Single Photon ◽

Signal To Noise Ratio ◽

Avalanche Photodiodes ◽

Single Photon Detection ◽

Linear Mode ◽

Detection Mode ◽

Artificial Star ◽

Zero Baseline ◽

Low Sensitivity ◽

Intensity Interferometer

ABSTRACT Optical intensity interferometry, developed in the 1950s, is a simple and inexpensive method for achieving angular resolutions on microarcsecond scales. Its low sensitivity has limited intensity interferometric observations to bright stars so far. Substantial improvements are possible by using avalanche photodiodes (APDs) as light detectors. Several recent experiments used APDs in single-photon detection mode; however, these either provide low electronic bandwidths (few MHz) or require very narrow optical bandpasses. We present here the results of laboratory measurements with a prototype astronomical intensity interferometer using two APDs observing an artificial star in continuous (‘linear’) detection mode with an electronic bandwidth of 100 MHz. We find a photon–photon correlation of about 10−6, as expected from the ratio of the coherence times of the light source and the detectors. In a configuration where both detectors are on the optical axis (zero baseline), we achieve a signal-to-noise ratio of ∼2700 after 10 min of integration. When measuring the correlation as a function of baseline, we find a Gaussian correlation profile with a standard deviation corresponding to an angular half-width of the artificial star of 0.55 arcsec, in agreement with the estimate by the manufacturer. Our results demonstrate the possibility to construct large astronomical intensity interferometers using linear-mode APDs.

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