Positions Of Stars Research Articles

Correction Method of Star Position Error for Splicing Star Simulator

Correction Method of Star Position Error for Splicing Star Simulator

Indonesian natural rubber export potential in European market

Indonesia is one of the largest natural rubber exporters in the world. On the other hand, the potential for natural rubber in the world market is enormous. The Asian continent is the largest market for Indonesian natural rubber, followed by American and European markets. Currently there have been many studies on the competitiveness of Indonesian natural rubber exports to the international market, but so far there has not been much research on the competitiveness and potential of rubber exports specifically to European countries. This study aims to determine the competitiveness and the potential of Indonesian natural rubber in European countries, namely Germany, France, and Spain. The method used in this study is descriptive analytics, meanwhile Revealed Comparative Advantage (RCA) was used to determine Indonesia’s competitiveness in each of the partner countries, on the other hand Export Product Dynamic (EPD) was used to determine the performance of Indonesian natural rubber in partner countries. The RCA index shows that Indonesia has competitive advantages in the partner countries, and the EPD matrix indicated that Indonesia is in a rising star position in the German, French and Spanish markets. To strengthen this position, Indonesia needs to increase their export value through the increase in production.

The development of projective metric method for analyzing star positions

In this work, the projective geometry method was used for analyzing star clusters. When carrying out the calculation procedures, it was considered that non-linear distortion factors had been removed from the measured stars’ coordinates. Determination of stars’ proper motions is of great practical importance, as the inertial coordinate system relies on catalogues of star positions, and it is necessary to be aware of the stellar reference marks’ time shift. In the practical part of the work, the breadboard simulation of the use of the proposed method for determining stars’ proper motions is performed. At the same time, it is supposed that at 90”/mm breadboard image scale the absolute values of proper motions do not exceed 0.050” over a period of 50 years. As result, determined that the standard deviation of the calculated proper motions μα , μβ from their true value is 0.0065 arcseconds for the first model (when the proper motions of the reference “stars” are negligible and equal to 0) and 0.0072 arcseconds or the second model (when the reference stars do have real proper motions). These values indicate the high accuracy of the used method.

THE MEXICAN ASTROGRAPHIC CATALOGUE AND CARTE DU CIEL PROJECT

The participation of Mexican astronomers in international projects dates back to the eighteenth century, when they observed the 1769 transit of Venus. More than a century later, they again participated in attempts to establish a precise value for the astronomical unit through the transits of Venus that occurred in 1874 and 1882. In 1887 Mexican astronomers were invited to join efforts to develop a multinational initiative known as the Carte du Ciel and International Astrographic Project, collaborating with 17 other observatories worldwide. Mexican astronomers obtained support from their Government, and they ordered telescopes from the Irish firm of Sir Howard Grubb and Company. An astrograph was used to photograph stars in Mexico's assigned sky zone (between declinations -10° and -16°) down to a limiting magnitude of 11 for the Astrographic Catalogue, and down to magnitude 14 for the Carte du Ciel. The Astrographic Catalogue photography began in February 1900, and the first of the plates for the Carte du Ciel was exposed in 1905. The Mexican astronomers had to overcome a number of serious difficulties, such as the Mexican Revolution of 1910-1920, which caused several delays and the loss of many personnel from the National Astronomical Observatory of Mexico, and then World War I, 1914-1918, which hindered the arrival of the photographic plates and interrupted communication with the Carte du Ciel Commission in Paris. Women usually were employed as 'computers' to measure the Astrographic Catalogue star positions. Between 1921 and 1962, seven volumes were published listing Mexican Astrographic Catalogue star positions. Mexican astronomers finished taking all of the Carte du Ciel plates, except for the -12° declination zone, but because of financial constraints only 375 plates were printed. Afterwards, from 1941, photography of the -13° zone was repeated in order to obtain stellar positions for proper motion studies. In March 1970 the mounting of the historic 33-cm Grubb astrograph and accompanying 25.4-cm guidescope was used at Miahuatlán, Oaxaca, together with a replacement tube assembly and objective to observe a total solar eclipse. Then from 1976 to 1979 three Astronomy students from the National University of Mexico reconstructed and renovated the original Grubb twin-telescope, which is now at Tonantzintla, near Puebla, and is used mainly for educational purposes.

The determination of Hipparchus' phenomena and their consistency with the Almagest star catalog

AbstractThe derivation of the phenomena in Hipparchus' Commentary on the phenomena of Aratus and Eudoxus from the star positions of his presumed star catalog is investigated under the assumption of their determination by a star globe. As most of Hipparchus' star coordinates are not available, they are reconstructed from the star catalog in Ptolemy's Almagest. Data consistent with the assumed determination of the phenomena are identified by a statistical method for the elimination of erroneous data; the parameters underlying this determination and the data accuracy are estimated by adjustment theory. The results indicate that, for the majority of the data under investigation, an accurate determination by a globe can be assumed. The estimated values of the parameters, the obliquity of the ecliptic and the observer's latitude, agree with information from historical sources and with values found in previous investigations of Hipparchus' data. Moreover, in most instances, the conducted analysis substantiates a strong relation between Ptolemy's and Hipparchus' star data under investigation.

Stellar occultations enable milliarcsecond astrometry for Trans-Neptunian objects and Centaurs

Context. Trans-Neptunian objects (TNOs) and Centaurs are remnants of our planetary system formation, and their physical properties have invaluable information for evolutionary theories. Stellar occultation is a ground-based method for studying these distant small bodies and has presented exciting results. These observations can provide precise profiles of the involved body, allowing an accurate determination of its size and shape. Aims. The goal is to show that even single-chord detections of TNOs allow us to measure their milliarcsecond astrometric positions in the reference frame of the Gaia second data release (DR2). Accurate ephemerides can then be generated, allowing predictions of stellar occultations with much higher reliability. Methods. We analyzed data from various stellar occultation detections to obtain astrometric positions of the involved bodies. The events published before the Gaia era were updated so that the Gaia DR2 stellar catalog is the reference, thus providing accurate positions. Events with detection from one or two different sites (single or double chord) were analyzed to determine the event duration. Previously determined sizes were used to calculate the position of the object center and its corresponding error with respectto the detected chord and the International Celestial Reference System propagated Gaia DR2 star position. Results. We derive 37 precise astrometric positions for 19 TNOs and four Centaurs. Twenty-one of these events are presented here for the first time. Although about 68% of our results are based on single-chord detection, most have intrinsic precision at the submilliarcsecond level. Lower limits on the diameter of bodies such as Sedna, 2002 KX14, and Echeclus, and also shape constraints on 2002 VE95, 2003 FF128, and 2005 TV189 are presented as valuable byproducts. Conclusions. Using the Gaia DR2 catalog, we show that even a single detection of a stellar occultation allows improving the object ephemeris significantly, which in turn enables predicting a future stellar occultation with high accuracy. Observational campaigns can be efficiently organized with this help, and may provide a full physical characterization of the involved object, or even the study of topographic features such as satellites or rings.

Estimating camera parameters from starry night photographs

We propose an efficient, specific method for estimating camera parameters from a single starry night image. Such an image consists of a collection of disks representing stars, so traditional estimation methods for common pictures do not work. Our method uses a database, a star catalog, that stores the positions of stars on the celestial sphere. Our method computes magnitudes (i.e., brightnesses) of stars in the input image and uses them to find the corresponding stars in the star catalog. Camera parameters can then be estimated by a simple geometric calculation. Our method is over ten times faster and more accurate than a previous method.

Precise Determination of Astronomical Azimuth by the Hour Angle Method of Multiple Meridian Stars

The method for precisely determining the astronomical azimuth using the local hour angle (LHA) of Polaris is only applicable in northern middle latitudes. In addition, the meridian star pair method is limited by the conditions of star selection and matching. A new hour angle method for multiple meridian stars is proposed, which is suitable for any part of the global region. When multiple south and north stars have been observed, the influence of longitude error and timing error on the azimuth is modified by linear regression. A precise astronomical position is not required, and there is no limit to the specific position of the meridian stars. Therefore, both the number of observable stars and work efficiency are greatly increased. Our experiment indicates that the results of the new method can reach the first-order accuracy level; i.e., the root mean square error (RMSE) is less than 0.5″, even when the amount of observed data is reduced to half that of the Polaris method.

Optimizing the location of multiple laser guide stars in ground layer adaptive optical systems

At present, the ground layer adaptive optical systems are using multiple laser guide stars arranged in regular polygons as reference targets to measure the effects of atmospheric turbulence. Obtaining the optimal position of laser guide stars becomes an interesting problem to analyze. This paper proposes a method to obtain the optimal position of laser guide stars by using a genetic algorithm as the optimization algorithm and a simplified geometry model of the ground layer adaptive optic system as the evaluation function. Furthermore, multi-process, Numba library, and multi-thread techniques methods are used to accelerate calculation speed. Based on these methods, real atmospheric turbulence profiles are used to analyze the relationship between the optimal position of laser guide stars with different numbers and the different atmospheric turbulence profiles from the same site, through an example of a ground layer adaptive optics system with 14 arcmin field of view. The results show that the optimal position of laser guide stars in the same site is almost the same and their statistically optimal positions are all regular polygon. Besides, we also find that the spatial resolution of turbulence profiles has strong effects to positions of laser guide stars, showing that the more equivalent layers in the measurement results, the closer the position distribution of laser guide stars is to the regular polygon.

The Market Position of Community-Based “Salak” Agrotourism in Yogyakarta Province

Agrotourism is a product in which its development needs to be accelerated because mostly located in rural areas, therefore, positive impacts are expected to emerge for the growth and development of rural economy. This research was aimed to know the market position and to formulate the community-based Salak Agrotourism development strategy in Yogyakarta Province. A descriptive qualitative method was used as the research method by implementing Boston Consulting Group (BCG) as the analysis instrument. It measured the rate of market growth and relative market share of the community-based ‘Salak’ Agrotourism toward non-community-based ‘Salak’ agrotourism in Yogyakarta Province. According to the results of BCG analysis, the market position of community-based ‘Salak’ Agrotourism in 2014 was in Question Mark position and in 2015 was in the Star position. Furthermore, in 2016 and 2017, the market position of community-based ‘Salak’ Agrotourism was in Cash Cow position. The Agrotourism development strategy that can be conducted is the concentric diversification strategy by developing and focusing on the Unique Selling Proposition (USP) in each agrotourism.

On the making of Ptolemy’s star catalog

The assumption that Ptolemy adopted star coordinates from a star catalog by Hipparchus is investigated based on Hipparchus’ equatorial star coordinates in his Commentary on the phenomena of Aratus and Eudoxus. Since Hipparchus’ catalog was presumably based on an equatorial coordinate system, his star positions must have been converted into the ecliptical system of Ptolemy’s catalog in his Almagest. By means of a statistical analysis method, data groups consistent with this conversion of coordinates are identified. The found groups show a high degree of agreement between Hipparchus’ and Ptolemy’s data. The value of the obliquity of the ecliptic underlying the conversion is estimated by adjustment and statistically agrees with Ptolemy’s value of this parameter. The results allow the assumption that Ptolemy’s coordinates were determined from Hipparchus’ coordinates by an accurate star globe or even by calculation. For a calculative derivation of ecliptical coordinates from equatorial ones, possible calculation methods are discussed considering the mathematics of the Almagest.

Marketing Strategy of Bengkulu Local Coffee: SWOT, BCG, and Benchmarking (Case Study: Kopi 1001)

The purpose of this study was to determine the strategy and position of the 1001 coffee brand and understand the market. The analysis used is SWOT analysis, BCG and Benchmarking. The results obtained, namely the results of the SWOT analysis, it is known that the main strategy for Kopi 1001 is the Growth strategy, where Kopi 1001 can increase sales with the advantages of its products and better use of promotions. BCG shows that Bengkulu City 1001 coffee is in a star position, which is in market share and high market growth. In this position, Kopi 1001 can implement a retrenchment strategy so that the business can survive in the face of competition from similar products. While the results of the benchmarking analysis show that 1001 coffee products have a distinctive robusta coffee taste and are safe for consumption, but product innovations need to be carried out that still maintain the characteristics of the coffee they have.

THE REFORMULATION OF ALGORITHM FOR CALCULATING STAR’S POSITION AS THE SIGN OF ISYA AND FAJR PRAYER TIMES

The position of the stars in the sky was used by Islamic Astronomy scholars as a sign of early Isya and Fajr prayers. This method is an alternative that was used in the past when there has not been an advanced time keeping tool like nowadays, especially for locations where syafaq and fajr shâdiq phenomena cannot be observed. Some of the algorithms used for calculating the star's position as a sign of early Isya and Fajr prayers are still fairly approximation (taqrîbi). So it requires a reformulation of the algorithm to make it is suitable for use in this period. This study resulted two offers of algorithms which are obtained by reformulating al-Buraidi’s method and al-Hâsib’s: First, the culmination of stars. Second, star’s altitude and azimuth. Accuracy test of reformulation of the algorithm compared by stellar observations shows that the results in reformulation of algorithm for calculating star’s position as the sign of early Isya and Fajr prayer time are quite accurate with accuracy in units of arc minutes.

The Strategic Positioning of Moroccan Seaports: An Application of the Boston Consulting Group Growth-share Matrix

Background: Under the current challenges of global and regional changing environments in the seaport industry faced by market players and the increase of competition among port business entities, the necessity of pursuing a competitive strategic positioning by strategic business units is a compulsory plan to ensure constructive and sustained growth. Aims and Objectives: In this context, the purpose of this study is to analyze the competitive position of the eight (largest, most important, busiest) seaports of Morocco in the four-years period from 2014 to 2017 using a dynamic portfolio analysis known as the Boston Consulting Group (BCG) matrix. This study aims to overcome the regional challenges that have a substantial impact on seaport activities by highlighting competitive strategic positioning, which will enable seaport operators to visualize the position of selected ports, monitor their progress, and predict the future trends of the studied ports. Results: The finding reveals the competitive strategic positioning of analyzed ports is varying over the studied period. Conclusion: The Tangier MED, Jorf Lasfar and Casablanca ports were found to be stars in 2017, while in 2015 they had a combined position of stars and cash cows. Other studied seaports were found to be in an unfavorable strategic position.

Bayesian Approach for Determining Microlens System Properties with High-angular-resolution Follow-up Imaging

Abstract We present the details of the Bayesian analysis of the planetary microlensing event MOA-2016-BLG-227, whose excess flux is likely due to a source/lens companion or an unrelated ambient star, as well as of the assumed prior distributions. Furthermore, we apply this method to four reported planetary events, MOA-2008-BLG-310, MOA-2011-BLG-293, OGLE-2012-BLG-0527, and OGLE-2012-BLG-0950, where adaptive optics observations have detected excess flux at the source star positions. For events with small angular Einstein radii, our lens mass estimates are more uncertain than those of previous analyses, which assumed that the excess was due to the lens. Our predictions for MOA-2008-BLG-310 and OGLE-2012-BLG-0950 are consistent with recent results on these events obtained via Keck and Hubble Space Telescope observations when the source star is resolvable from the lens star. For events with small angular Einstein radii, we find that it is generally difficult to conclude whether the excess flux comes from the host star. Therefore, it is necessary to identify the lens star by measuring its proper motion relative to the source star to determine whether the excess flux comes from the lens star. Even without such measurements, our method can be used to statistically test the dependence of the planet-hosting probability on the stellar mass.

Astrometric study of Gaia DR2 stars for interstellar communication

AbstractWe discuss the prospects of high precision pointing of our transmitter to habitable planets around Galactic main sequence stars. For an efficient signal delivery, the future sky positions of the host stars should be appropriately extrapolated with accuracy better than the beam opening angle Θ of the transmitter. Using the latest data release (DR2) of Gaia, we estimate the accuracy of the extrapolations individually for 4.7 × 107 FGK stars, and find that the total number of targets could be ~107 for the accuracy goal better than 1″. Considering the pairwise nature of communication, our study would be instructive also for SETI (Search for Extraterrestrial Intelligence), not only for sending signals outward.

Deep into the core of dense star clusters: an astrometric and photometric test case for ELT

ABSTRACT We present a novel analysis of a young star cluster in the Large Magellanic cloud, R136-like, as seen by the Extremely Large Telescope (ELT). The main aim of this study is to quantify precision and accuracy of stellar proper motion measurements in crowded field when using an ELT working at its diffraction limit. This can serve as a reference study for future development of ELT scientific cases. In particular, we investigate our future ability to detect the dynamical signature of intermediate-mass black holes (IMBHs) with mass ∼104 M⊙ through detailed measurements of stellar proper motions. We have simulated two N-body dynamical cluster models with and without an IMBH. For each model, we have chosen two snapshots temporally spaced by 5 yr. Stellar fluxes in IJHK filters and star positions have been used to create ELT mock images for both single- and multiconjugate adaptive optics observing modes following the requierements given by ESO technical specifications for the first light imager. These images have been analysed using a classical software for seeing-limited data reduction, daophot/allstar. We make accurate photometry till the very faint pre-main-sequence stars, i.e. depending on the adaptive optics (AO) mode, magnitudes down to K ∼ 24 mag (single-conjugate AO) or K ∼ 22 mag (multiconjugate AO) in a total integration time of 20 min on target. Although daophot suite of programs is not devoted to precise astrometry, the astrometric accuracy is impressive, reaching few μas yr−1 or km s−1. In these assumptions, we are able to detect the IMBH signature at the centre of the cluster.

Impact of a companion and of chromospheric emission on the shape of chromosome maps for globular clusters

Context. Globular clusters (GCs) host multiple populations of stars that are well-separated in a photometric diagram – the chromosome map – built from specific Hubble Space Telescope (HST) filters. Stars from different populations feature at various locations on this diagram due to peculiar chemical compositions. Stars of the first population, with field star-like abundances, sometimes show an unexpected extended distribution in the chromosome map. Aims. We aim to investigate the role of binaries and chromospheric emission on HST photometry of globular clusters’ stars. We quantify their respective effects on the position of stars in the chromosome map, especially among the first population. Methods. We computed atmosphere models and synthetic spectra for stars of different chemical compositions, based on isochrones produced by stellar evolution calculations with abundance variations representative of first and second populations in GCs. From this we built synthetic chromosome maps for a mixture of stars of different chemical compositions. We subsequently replaced a fraction of stars with binaries, or stars with chromospheric emission, using synthetic spectroscopy. We studied how the position of stars is affected in the chromosome map. Results. Binaries can, in principle, explain the extension of the first population in the chromosome map. However, we find that given the binary fraction reported for GCs, the density of stars in the extended part is too small. Another difficulty of the binary explanation is that the shape of the distribution of the first population in the chromosome map is different in clusters with similar binary fractions. Also, the decrease of the binary fraction with radius is not mirrored in the shape of the chromosome map. Additionally, we find that the contribution of chromospheric emission lines to the HST photometry is too small to have an observable impact on the shape of the chromosome map. Continuum chromospheric emission has an effect qualitatively similar to binaries. Conclusions. We conclude that binaries do have an impact on the morphology of the chromosome map of GCs, but they are unlikely to explain entirely the shape of the extended distribution of the first population stars. Uncertainties in the properties of continuum chromospheric emission of stars in GCs prevent any quantitative conclusion. Therefore, the origin of the extended first population remains unexplained.

Indonesian Clove Competitiveness and Competitor Countries in International Market

Trade liberalization is currently demanding every country to increase the competitiveness of its products. Indonesia as the largest clove producer in the world has a major competitor in the international market. This study aims to determine the competitiveness of Indonesia's clove exports and competing countries in the international market and determine the factors that affect its competitiveness. The data used in this study are secondary data from five major producing countries namely Indonesia, Madagascar, Tanzania, Sri Lanka, and Comoros during the period 2000-2017 sourced from UNComtrade, FAO and the World Bank. Competitiveness is measured by Revealed Comparative Advantage (RCA), Acceleration Ratio (AR) and Export Product Dynamic (EPD) while the factors that affect competitiveness are used panel data regression methods using E-Views software. The results showed that Indonesia had the lowest RCA index, the AR value showed Madagascar and Tanzania were able to capture market share in the international market and the EPD value showed that all countries occupied the rising star position except Sri Lanka in the falling star position. Panel data regression analysis results show that the market share and GDP variables significantly influence the competitiveness of the main clove producing countries while the production variables and export prices do not significantly influence the country's competitiveness. The government must dare to take policies to limit clove imports and increase exports.

Astrometric effects of gravitational wave backgrounds with nonluminal propagation speeds

A passing gravitational wave causes a deflection in the apparent astrometric positions of distant stars. The effect of the speed of the gravitational wave on this astrometric shift is discussed. A stochastic background of gravitational waves would result in a pattern of astrometric deflections which are correlated on large angular scales. These correlations are quantified and investigated for backgrounds of gravitational waves with sub- and super-luminal group velocities. The statistical properties of the correlations are depicted in two equivalent and related ways: as correlation curves and as angular power spectra. Sub-(super-)luminal gravitational wave backgrounds have the effect of enhancing (suppressing) the power in low-order angular modes. Analytical representations of the redshift-redshift and redshift-astrometry correlations are also derived. The potential for using this effect for constraining the speed of gravity is discussed.