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91	COMPUTATIONAL SCIENCES	ABS-189
Molecular Properties of Chitosan Receptor for The Ligand Vitamin C and Curcumin Nayla Zahra Kamalia(1), Dwi Hudiyanti(1), Khairul Anam(1a), Cholid Djunaidi(1b), Vivitri Dewi Prasasty(2), Parsaoran Siahaan(1*) 1) Physical Chemistry Laboratory, Department of Chemistry, Faculty of Sciences and Mathematics, Diponegoro University, Semarang, Indonesia a) Organic Chemistry Laboratory, Department of Chemistry, Faculty of Sciences and Mathematics, Diponegoro University, Semarang, Indonesia b) Analytical Chemistry Laboratory, Department of Chemistry, Faculty of Sciences and Mathematics, Diponegoro University, Semarang, Indonesia 2) Faculty of Biotechnology, Atma Jaya Catholic University of Indonesia, Jakarta, Indonesia. Abstract Chitosan has been widely used as an adsorbent and drug delivery because it has many attractive properties such as biocompatible, biodegradable, non-toxicity, and its ability to interact with other molecules due to the present of very reactive amino (-NH2) and hydroxyl (-OH) groups in its backbone. In this study chitosan with variations of monomers 3,5, 10 and 15 have been modeled by in silico approach using molecular dynamic and molecular docking to study its properties and the interaction between chitosan, vitamin C and curcumin. The result showed that the interaction energy increases with increasing number of monomers, which means that the complex bonds are more stable, because the number of binding sites formed is increasing. The binding energy of chitosan-15...vitamin C is -4,0220 kcal/mole and chitosan-15...curcumin -5,7260 kcal/mole. The molecular dynamic simulation explained that the stability of chitosan...vitamin C and chitosan...curcumin complexes was affected by the binding energy. In this study, sequential docking was carried out to study the effect of adding other ligands to the same receptor to weaken or strengthen the interaction between the receptor and the ligand, so that it can be used as a basis for studying its application as an adsorbent and drug delivery. Keywords: Chitosan, Molecular Docking, Molecular Dynamic, Sequential Docking Share Link | Plain Format | Corresponding Author (Nayla Zahra Kamalia)

92	COMPUTATIONAL SCIENCES	ABS-196
Generalisation of Eisenstein Criterion in Interactive Theorem Prover Mizar Leonardus Reinaldy Christianto (a), Irawati (b) (a) Master of Teaching of Mathematics, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia leonardusrenaldi[at]gmail.com (b) Mathematics, Bandung Institute of Technology Jalan Ganesha 10, Bandung 40132, Indonesia irawati[at]itb.ac.id Abstract Technological developments offer digitization in various aspects that aim to make it easier for users to access it. One example of digitization currently being developed in the field of mathematics is the interactive theorem prover program - Mizar. Mizar is one of the technological developments designed for mathematicians to verify proofs and document them in the Mizar Mathematics Library. It is intended that a collection of documented articles can become a modern digital encyclopedia in the field of mathematics. Mizar was first introduced in Poland in 1973 and is currently being developed in Japan and China, while in Indonesia there are still not many people who know about the Mizar program. So, in this study, the Mizar program will be introduced along with an explanation regarding the steps to operate it. This research is also part of the author^s experience when working with Mizar in verifying the accuracy of the proof of the generalization of the Eisenstein criterion theorem. Keywords: Mizar, Application, Program, Mathematics Share Link | Plain Format | Corresponding Author (Leonardus Reinaldy Christianto)

93	COMPUTATIONAL SCIENCES	ABS-217
Robust inversion of 1D magnetotelluric data using Huber Loss function Elfitra Desifatma, I Gede Putu Fadjar Soerya Djaja, Prihandhanu Mukti Pratomo, Enjang Jaenal Mustopa, and Wahyu Srigutomo* Faculty of mathematics and natural sciences, Bandung Institute of Technology Jl. Ganesha 10, Bandung 40132, Indonesia Email of corresponding author: *srigutomo[at]itb.ac.id Abstract In this study, a robust 1D inversion was performed on magnetotelluric (MT) data by utilizing the Huber loss function. In the MT method, impedance values (Z) obtained from the ratio between the electric field (E) and the magnetic field (H) that are perpendicular to each other are used to get subsurface information in the form of electrical resistivity variation with depth. Forward modeling of the 1D MT responses is carried out by recursively calculating Z values. Robust inversion is performed by using the Huber loss function as an objective function to minimize the difference between calculated data and observation data. Huber loss function combines squared loss and absolute loss to anticipate the presence of outliers in MT observation data. Robust inversion is performed on synthetic data with additional noise and real field data. The robust inversion scheme is successful in overcoming the existence of outliers and estimating the actual model parameters, both on synthetic data that has sufficiently large noise and on real field data. Keywords: Magnetotelluric, Electromagnetic, Robust inversion, Huber Loss Function Share Link | Plain Format | Corresponding Author (Elfitra Desifatma)

94	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-256
Preliminary Study of Effective Pore Connectivity Index (EPCI) to Detect Impermeable Layers in Porous Rock Budi Dharmala Saputra (a*), Fourier Dzar Eljabbar Latief(a) (a) Physics of Complex Systems, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Jalan Ganesha 10, 40132, Bandung, Indonesia Abstract This study investigates the use of EPCI, a computationally calculated parameter, to predict pore connectivity in 3D digital rock samples. EPCI is used as an initial screening tool to determine whether rock samples are permeable or impermeable. This screening is useful in the processing of digital rock samples that will have their permeability calculated using the Lattice Boltzmann Method (LBM). LBM implemented in the Palabos library has been found to be unsuccessful in determining if a sample is impermeable. The study starts by using EPCI to verify simple cases consist of simple pipe models with predetermined connectivity at certain direction. EPCI is then tested on actual rock samples. The rock sample images used vary in levels of connectivity. To demonstrate that EPCI is able to detect the presence of an impermeable layer, a model of impermeable layer is added into a real sample. The results of the study show that the EPCI algorithm can be used to calculate the connectivity between pores in rock samples with good connectivity and can detect the presence of impermeable layers in rock samples. Keywords: EPCI, permeability, pore connectivity, impermeable layer Share Link | Plain Format | Corresponding Author (Budi Dharmala Saputra)

95	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-3
Principal Component Analysis to Modeling Cosmic Rays Intensity Based on Variation Solar Activity and Interplanetary Plasma Parameter Annisa Novia Indra Putri (a,b*), Dhani Herdiwijaya (a), Taufiq Hidayat (a) a) Astronomy Department, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, West Java, Indonesia *annisa.putri[at]sap.itera.ac.id b) Atmospheric and Planetary Sciences Study Program, Institut Teknologi Sumatera, South Lampung, Lampung, Indonesia Abstract Studies of the correlation between the intensity of cosmic rays and the number of sunspots has been carried out for a long time. The various studies that have been carried out have shown an anti-correlation between the intensity of cosmic rays and the number of sunspots, where there are some differences in the time lag in different solar cycles. The differences that arise until now are still a question. In this paper, modeling analysis will be carried out using various parameters from solar activity and interplanetary space such as the number of sun- spots, solar wind speed, Interplanetary Magnetic Field (IMF), the Heliospheric Current Sheet (HCS) tilt, and halo CME speed. The data has time intervals that vary from 1749 to 2022, with daily to monthly time resolutions. Analysis of the relationship between the intensity of cosmic rays with these five parameters using the Principal Component Analysis (PCA) method. The result shows that all parameters have anti-correlation with the cosmic rays intensity. Also, they have the same effect in contributing cosmic rays modulation. Keywords: Cosmic Rays Intensity, Solar Activity, Interplanetary Plasma, PCA Share Link | Plain Format | Corresponding Author (Annisa Novia Indra Putri)

96	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-6
RAOS: REBOUND-based Customizable Codes for Asteroid Orbital Simulation M. Rezky, E. Soegiartini, M.I. Hakim and A.S. Hutasoit Astronomy Research Group, Institut Teknologi Bandung, Indonesia Abstract RAOS is an N-body simulation program intended for the orbital simulation of asteroids, which utilised Python-based REBOUND and REBOUNDx code packages. It was designed for studying the orbital dynamics of asteroids in our Solar system, with data produced in one simulation run such as ephemerides calculation of target asteroid, Kozai parameter, and resonance-related parameters. For ephemerides calculation, RAOS also provides options to include calculations for 243 (3^5) asteroid clones to determine the orbital stability of the target asteroid within 1-sigma uncertainty of the nominal orbit value. The modular and tailored nature of REBOUND and REBOUNDx packages makes it easy to build customisable code to accommodate specific needs for different types of target asteroids and their respective orbital studies. Besides the ability to modify integrator, collision, and other simulation settings, RAOS also provides ways to include non-gravitational influences such as post-Newtonian and radiation forces. In this paper, we discuss the general algorithm, its limitations, and opportunities for further development that will benefit the development of Solar system dynamical studies. We also present results from the RAOS program on several Atira asteroids that were subject to our separate research project, with relative errors within the expected theoretical values that prove the accuracy of this program. As the RAOS program is also structured to allow modifications for further developments, it will also be beneficial for the advancement of computational astrophysics for future researchers and students. Keywords: Asteroid, Ephemerides, N-body simulation, Orbital dynamics Share Link | Plain Format | Corresponding Author (Muhammad Rezky)

97	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-10
The Relation between Stellar Pulsation and Emission Line Profiles of HD 144470 Muthia Dewi (a), Aprilia (b*), Irfan Imaduddin (a) a) Astronomy Study Program, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung, 40132, Indonesia b) Astronomy Research Division and Bosscha Observatory, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung, 40132, Indonesia *aprilia[at]as.itb.ac.id Abstract In this work, we analyse star HD144470 (\(\omega^{1} sco\)), which is a pulsating star that shows emission lines in its spectrum, using photometric and spectroscopic data. The emission line profiles appear at \(\lambda\) 6,506.2 Angstrom (Ce II-line) and \(\lambda\) 6,718.0 Angstrom (Ca I-line). We observe these spectra at Bosscha Observatory, Indonesia, in 2019 and 2020. We use Lomb Scargle Periodogram method to calculate the variability periods in photometric data (9.11-day- 6.65-day and 7.11-day period). Then, we validate it with the appearance of emission lines on the June 29th, 2020 spectrum of the entire spectra. Only the 9.11-day period is proved valid across the spectra. It answers the relation between the period of variability in photometric data and the appearance of the emission line profile of Ce II and Ca I, namely a period of 9.11 days. Keywords: Pulsation- Emission Line- Period- Oscillation in Stars- Variability Share Link | Plain Format | Corresponding Author (Muthia Dewi)

98	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-13
Spatial Model of Ionospheric Vertical Total Electron Content for Low-Latitude Indonesia Region Based on Multiple Regression Analysis Asnawi Husin, Rizal Suryana, Ayu Nur Safii, Varuliantor Dear, Sri Ekawati, Angga Y Putra, Nia Safitri and Buldan Muslim National Research and Innovation Agency - BRIN Abstract The interaction of trans-ionospheric radio waves of Global Navigation Satellite Systems (GNSS) signals with the plasma ionosphere lead to propagation delay that has impact on accuracy degradation of position measurements. The ionospheric propagation delay has proportional to the integrated electron density (Total Electron Content - TEC) along the ray path. In order to monitor and understand the physics that control the dynamics of the ionospheric TEC and regarding to ionosphere delay, number of global and regional ionospheric model and data mapping has been developed. This paper, attempt to mapping the regional ionospheric TEC over Indonesia sector (90oE-140oE and 12o N 15o S) by using an analysis of multiple regression. The main method is multiple regression of TEC based on ionospheric pierce point (IPP) is developed on the basis of polynomial low order scheme driven by GNNS data from the Indonesian Continuously Operating Reference Station (INACORS) network provided by the Indonesian Geospatial Information Agency (Badan Informasi Geospasial - BIG). The accuracy and quality of the TEC mapping technique have been validated through cross comparison with individual GNSS station observations, the International Reference Ionosphere (IRI2016) model and global ionosphere maps from IGS-GIM. The verification results in general that TEC model by multiple polynomial regression indicated comparable with TEC by kriging method and GIM IGS. Keywords: Ionosphere, spatial, TEC Share Link | Plain Format | Corresponding Author (Asnawi Husin)

99	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-14
Comparison of ARIMA, LSTM, BiLSTM and GRU for Prediction Model of S4 over Kototabang-Indonesia Faruk Afero (a*), Falin Wu (b*), Varuliantor Dear (*c) a) SNARS Laboratory, School of Instrumentation and Optoelectronic Engineering Beihang University Beijing, P.R.China *farukafero[at]buaa.edu.cn b)SNARS Laboratory, School of Instrumentation and Optoelectronic Engineering Beihang University Beijing, P.R.China *falin.wu[at]buaa.edu.cn c) Research Center for Space Science National Research and Innovation Agency Bandung, Indonesia *varuliantor.dear[at]brin.go.id Abstract An accurate prediction of time series data is important for space weather information services including for forecasting ionospheric scintillation. Scintillation activity usually increases with increasing solar activity. During periods of maximum solar activity, the ionosphere structure usually changes dramatically which will significantly affect radio wave propagation. It is challenging to build a prediction model of ionospheric scintillation under extreme space weather conditions. In this paper, we conduct a comparison study of scintillation prediction using Autoregressive Integrated Moving Average (ARIMA), Long Short-Term Memory (LSTM), Bidirectional LSTM (BiLSTM), and Gated Recurrent Unit (GRU). In order to take a challenge, a month data of scintillation over Kototabang-Indonesia (0.3S -100.35E) on January 2014 which the strong solar activity was happening is used as a training dataset. A qualitative comparison between the predicted output and the actual future was conducted to evaluate the model performance. The prediction results using these four methods show a reasonable scintillation model and BiLSTM has the best performance among the others methods. These results indicate that BiLSTM has the potential to be applied to predicting the scintillation by considering the lowest RMSE and MAE are 0,0900 and 0,1011 respectively. Keywords: ARIMA, BiLSTM, GRU, Ionospheric Scintillation, LSTM, Machine Learning, Space Weather, Time Series Prediction. Share Link | Plain Format | Corresponding Author (Faruk Afero)

100	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-18
Dynamical and Parameter Constraints of Dark Energy Dynamics Model with \(\alpha\)-Attractor Potential Scalar Field Aulia Taqiaturrahmah, Hesti Retno Tri Wulandari, Fargiza Abdul Malikul Mulki Institut Teknologi Bandung Abstract Observations of type Ia supernovae have shown that the expansion of the universe is accelerating. Since generic matters can not induce acceleration, dark energy as an additional component with negative pressure has been proposed. Cosmological constant is the simplest dark energy model, however, it suffers from energy scale and coincidence problems. Aiming at alleviating cosmological constant problems, various models of dynamical dark energy in the form of scalar fields have been put forward, such as quintessence, k-essence, and phantom field. A model is considered more successful if it accommodates a broader range of initial values (basins of attractions) and evolves convergently to the late time conditions. Unfortunately, the proposed scalar fields still have relatively narrow basins of attractions. Therefore, -\alpha--attractors have been proposed, and are predicted to have vast basins of attractions with their attractor property. The dynamical behavior of \(\alpha\)-attractors is governed by its potential parameters. The parameter \(\alpha\) is responsible for the scaling, while the two power parameters, \(p\) and \(n\), dictate the shape of the potential model. Additionally, the initial value of the field determine the evolutionary track and how it meets observational constraints for a given set of parameters. Another feature of this model is the \(c\) parameter determined by the closure relation in fulfilling the energy density budget of the universe. A stability test was performed using an autonomous method, describing the behaviors around critical points. Physically interpreted, the \(\alpha\)-attractor evolves following the equation of cosmic dynamics, which goes through generic matter- and dark energy-dominated eras. The results for Starobinsky potential, i.e., the \(\alpha\)-attractor potential model with \(\alpha=1\), \(p=2\), and \(n=1\), shows that there exists a stable cosmic acceleration solution. We used supernovae Ia and BAO data to perform a statistical analysis employing Markov Chain Monte Carlo. We found that the data support a solution with \(\alpha=2.848\), \(p=3.077\), and \(n=4.929\) for the initial value of \(\phi_{ini}=2.59\). Keywords: basin of attraction, dark energy, scalar field, \(\alpha\)-attractor Share Link | Plain Format | Corresponding Author (Aulia Taqiaturrahmah)

101	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-20
Design of Mobile and Robotic Telescope Mount with Dual Equatorial & Alt-Azimuth System Hanif Nanda Syahputra (a*), Dhani Herdiwijaya (b) a) Master Program in Civil Engineering, Sebelas Maret University, Indonesia *hanifnanda.s[at]gmail.com b) Department of Astronomy, Bandung Institute of Technology, Indonesia Abstract Light pollution is getting worse in many places. It has reduced the location of the dark sky and changed the way for observing the clear night sky. Traditional telescopes have been a heavier system and very difficult for beginners to use and find the celestial object they want to see. Moreover, people must observe the new moon in the near horizon to determine the time of worship for Muslims. They need a portable and good balance telescope mounting. The telescope design with a mechanical structure and mounting based on the operation of the equatorial system or the Alt-Az was developed. We focused on mounting without the need for counter weight and added a computer system to make it easier to move and connect to other devices. The challenge in realizing this tool is that the change in position on the mounting axis causes the magnitude of the torque to vary greatly. The mounting should balance the change of direction of the gravitational load to the orientation of the mounting structure. In this research, the finite element method (FEM) was used to predict the number of deformation variations that occur on the mounting. So, it can provide a rational basis for knowing the performance of the mounting structure when pointing and tracking. After challenging the above problems, we constructed and tested the prototype of the mounting. The performance of the mounting revealed good results. Keywords: telescope mounting- finite element method- design Share Link | Plain Format | Corresponding Author (Hanif Nanda Syahputra)

102	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-23
Geochemical Approach for Anak Krakatau Eruption Patterns Windi Anarta Draniswari 1, Aditya Pratama 1, Dini Nurfiani 1, Taufik Ismail 1,2, Wilfridus Ferdinando Supriyadi Banggur 1, Putu Billy Suryanata 1,3, Muhammad Zain Tuakia 4 1 Center of Geological Disaster Research, Indonesia Agency of Research and Innovation, Bandung 40135, Indonesia 2 Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung 40132, Indonesia 3 Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Bandung 40132, Indonesia 4 Research Center for Geological Resources, National Research, and Innovation Agency (BRIN), Bandung 40135, Indonesia Abstract Mt. Anak Krakatau is one of the most active volcanoes located in Sunda Strait. It is vital to understand the temporal and chemical evolution of Mt. Anak Krakatau in order to forecast a future eruption. This paper aims to analyze the trend of eruption probabilities through a statistical review. We use the rock geochemistry database and eruption histories to describe the link between magma evolution and volcano eruption. The contributions of each parameter to the repose length were examined through the log-likelihood. The statistical analysis reveals that the Volcano Eruption Index (VEI) and the time of the eruption are correlated with the chemical composition of the magma. The eruption could alter the dynamics of the magma chamber during the repose period and be recorded as the petrology and geochemical characteristic of rocks. The variability of the geochemical concentration of SiO2, TiO2, Al2O3, or MgO correlates with the repose length and the mixing process in the magma chamber. This finding can be used to reinforce the petrology and geochemistry data to identify the possible composition trends and the behavior of the volcano. Hence there is a limitation for eruption forecasting related to the morphological changes and displacement of the eruption vent. Keywords: Anak Krakatau, geochemistry, eruption Share Link | Plain Format | Corresponding Author (Windi Anarta Draniswari)

103	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-27
Photometric Observation of Defunct Satellites Using Small Telescopes: Preliminary Results Abdul Rachman (a*), Thomas Djamaluddin (a), Alessandro Vananti (b) a) Research Center for Space, National Research and Innovation Agency (BRIN), Indonesia *abdr001[at]brin.go.id b) Astronomical Institute University of Bern (AIUB), Switzerland Abstract Light curve analysis of space debris is one of the methods that is applicable to identify their attitude in orbit. Detailed information of debris characteristics is important, among other things, to mitigate its hazards to operational satellites and people on Earth. Kupang Space Observational Station at Tilong (as supporting facility for Timau National Observatory) currently operates several small optical telescopes with CCD camera and robotic capability. Those telescopes are suitable for monitoring space debris. A set-up for photometric observation has been configured and some preliminary results have been obtained and compared to the previous results from the same objects contained in AIUB Light Curve Database which is maintained by the Astronomical Institute of the University of Bern (AIUB) in Switzerland. In the case of defunct GLONASS satellites, as a sample, our limited result shows consistency with the reference. It was able to show similar light curve morphology with the ones in the AIUB database. Typically, four peaks appear in a phase diagram of decommissioned GLONASS satellites which resemble their four sides. Physically, a quasi-periodic light curve indicates rotating debris, while a complex light curve indicates a tumbling debris likely due to collision or other disturbances. This result, while only preliminary, is inspiring considering that the primary telescope objective of the current set-up is only 20 cm in maximum compared to the reference database which is based on a 1-m telescope. Keywords: Photometric observation- Space debris- Defunct satellites Share Link | Plain Format | Corresponding Author (Abdul Rachman)

104	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-34
The Relation between Solar Flares and Cosmic Rays Intensity during 23rd and 24th Solar Cycle A Z Rozzykin, E A Ariyani, A B Wahidin, A N I Putri Department of Atmospheric and Planetary Science, Institut Teknologi Sumatera Abstract Cosmic rays are high-energy particles originating from the stars in our galaxy and distant galaxies. These particles can infiltrate the Earth^s atmosphere and affect its magnetic field. Some previous studies showed that cosmic rays also influence aerosols and cloud formation. This study analyzes the relationship between solar flare activity and cosmic rays intensity. As mentioned earlier, we use the Pearson correlation coefficient to evaluate the correlation between the variables. We will use the solar flare data on C-, M-, and X-class flares and cosmic ray counts from 1996 to 2021, which coincides with the 23rd and 24th solar cycles. Our preliminary study showed that the number of X-class flares is highly anticorrelated to cosmic ray counts. In the meantime, we will also investigate the C- and M-class flares to better know the phenomenon^s details. Keywords: Cosmic rays- Solar activity- Solar flares Share Link | Plain Format | Corresponding Author (Achmad Zainur Rozzykin)

105	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-43
Retro-MACHO Lensing of Schwarzschild Black Hole in The Solar System Neighborhood Rafa S. Nadhil, Premana W. Premadi Astronomy Study Program, FMIPA, Institut Teknologi Bandung Bosscha Observatory, FMIPA, Institut Teknologi Bandung Abstract Specific case of gravitational lensing configuration where light trajectory is deflected and turned around resulting in an image that can be seen by an observer located between the lens and the light source is called retrolensing. We do computational retrolensing experiment using our Sun as the light source, Earth as the observer, and a Schwarzschild black hole acting as the lens located at several distance points in the periphery of the solar system and calculate the apparent magnitude of the lens images. We found that the most prominent effect came from the variation of mass while the effect of varying the distance between observer and lens is not significant as the range that we consider is still in the neighbourhood of our solar system. We also found that the image brightness peaked at perfect alignment and falls off rapidly until around 0.0378 radians and continue to decrease more gently towards larger angle. Even though the computed image brightness in general is still too low for the current observational technology, observation is still possible using retrolensing method to discover larger mass black holes if they happened to be in the solar system neighbourhood. Keywords: Gravitational Lensing, Black Hole, Solar System Share Link | Plain Format | Corresponding Author (Rafa Syauqin Nadhil)

106	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-46
BVR Photometric Observation of SX Phoenicis Sulthan J Djumari (a*), Robiatul Muztaba (a,b,c), Muhammad R Kurniawan (a), Hendra Agus Prastyo (a,d), Alka Budi Wahidin (a,d), Hakim L Malasan (a,c,d), Ridlo W Wibowo (a,d) Aditya Abdillah Yusuf (d) a) Department of Atmospheric & Planetary Sciences, Faculty of Science, Institut Teknologi Sumatera, Lampung 35365, Indonesia *sulthan.119290031[at]student.itera.ac.id b) Doctoral Program in Astronomy, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No.10, Bandung 40132, Indonesia c) Astronomy Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung 40132, Indonesia d) Observatorium Astronomi ITERA Lampung (OAIL), Institut Teknologi Sumatera, Lampung 35365, Indonesia Abstract Photometric observation of SX Phoenicis [HD 223065, RA(J2000.0) = 23h 46m 32.8s, Dec(J2000.0) = -41d 34^ 54.7^] was made on September 2022, using the 0.25-m Ritchey-Chretien reflector telescope equipped with a CMOS ZWO ASI 533MM Pro camera at ITERA Astronomical Observatory. Analyses of the light curves were performed. We used set of BVR filters to secure the light curves. In Addition, we obtained photometric data of SX Phoenicis from literature to compare with our data. Lomb-Scargle periodogram analysis was performed on the photometric data to detect periodicity and to deduce the period. Values of the O - C from the observation were deduced. The apparent magnitudes were corrected to the atmospheric extinction. Intrinsic colours of B - V and V - R were derived and the physical parameters of this star have been determined from the light curve. Keywords: period analysis- technique: photometry- stars: SX Phoenicis- variable stars. Share Link | Plain Format | Corresponding Author (Sulthan Julieri Djumari)

107	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-51
Geomorphology of Cimaung Valley: Implications for Disaster Mitigation in Cimaung Sub-District and Surroundings Area, Bandung District Muhammad Agung Gumilar (a*), Riyan Hidyatulloh (a), Taufik Ismail (b,c), Billy Petrus Wehelmus (a), Rifo Rausyan Fikri (a), Elvis Okvianta (a), Dwigko Kurniawan Wandray (a), Mirzam Abdurrachman (b) a) Department of Geology, Indonesia College of Mineral and Technology, Bandung 40263, Indonesia *gumilara48[at]gmail.com b) Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung 40132, Indonesia c) Center of Geological Disaster Research, Indonesia Agency of Research and Innovation, Bandung 40135, Indonesia Abstract Cimaung Village is one of the villages part of the Cimaung District which is in the southern part of Bandung. Location is right at the confluence of three remaining volcanoes namely Mount Malabar, Mount Tilu and Mount Tanjaknangsi. Its existence in this valley is very vulnerable to geological disasters, such as floods, landslides, etc. Residual activity of the three volcanoes greatly influences the geomorphological conditions. Rocks produced from volcanic activity play an important role in the formation of a distinctive geomorphology. The rocks in the Cimaung area and its surroundings are the result of volcanic activity such as lava, lava and pyroclastic. Geomorphological analysis was carried out by analyzing river flow patterns, topographic maps, slopes and landsat imagery in the form of DEM (Digital Elevation Model) as well as direct observations in the field. Results of the geomorphological analysis are poured into geomorphological maps and maps of disaster-prone areas. Geomorphological unit in the study area consists of 11 (eleven) geomorphological units, in which morphological changes are still continuing today. Main control for significant morphological changes is controlled by human activities, weathering and land clearing will continue to this day. Keywords: Geomorphology- Disaster Mitigation- South Bandung Share Link | Plain Format | Corresponding Author (Muhammad Agung Gumilar)

108	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-312
GPR Data Processing Workflow for River Bridge Column Measurement Gunawan Handayani 1Laboratory of Earth Physics and Complex Systems Bandung Institute of Technology Abstract The dimension of a column of a river bridge is very important in Civil Engineering evaluation. But for an old bridge of a deep river, the Musi River of Palembang, the measurement of dimension columns became a problem. The built-in drawing was not available. The columns and the pile caps are under the water surface, which required the nondestructive test to determine the dimensions. We selected the Ground Penetrating Radar to carry out the measurements. After the measurements, we processed the GPR data. It needed trial and error to implement a data processing workflow to obtain an optimum image of sub-water surface columns. We start with: Move start time, Subtract-DC-shift. Subtract-mean (Dewow), Bandpass frequency filtering, and Background removal. Later we apply the multiple reflection suppression process, which dominates the image. Keywords: Ground Penetrating Radar, river, old bridge Share Link | Plain Format | Corresponding Author (Gunawan Handayani)

109	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-66
Understanding the Historical Pattern of Reentered Artificial Space Objects Fazira Azzahra Huwaidaa(a), Abdul Rachman(b) (a) Atmospheric and Planetary Science Program, Sumatra Institute of Technology, South Lampung, Indonesia (b) Research Center for Space, National Research and Innovation Agency (BRIN), Indonesia Abstract Solar activity primarily affects atmospheric density especially in the thermosphere. An increase in the solar activity will cause orbiting satellites in the region experience an increase in the atmospheric density. This will enhance the level of atmospheric drag on the satellites which accelerate their decay rate. Therefore, superficially people will assume that solar activity with its eleven-year periodicity will correlate positively strong with the historical number of reentered artificial space objects. However, in this paper we explain that this is not the case. We also explain how the number of newly added objects in the low Earth orbit plays a significant role in affecting the historical pattern of reentered artificial space objects. Keywords: Solar activity, artificial space objects, orbital decay Share Link | Plain Format | Corresponding Author (Fazira Azzahra Huwaidaa)

110	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-67
DETERMINING THE DISTANCE OF LOOP I STRUCTURE AT SOUTHERN GALACTIC LATITUDE Ilham Maulana (1) & Lucky Puspitarini (2*) 1) Bosscha Observatory, Faculty of Mathematics and Natural Sciences (FMIPA), Institut Teknologi Bandung, Jl. Peneropongan Bintang No. 45, Lembang 40391, Indonesia 2) Astronomy Research Division and Bosscha Observatory, FMIPA ITB, Jalan Ganesha 10, Bandung 40132, Indonesia *Email: lucky.puspitarini[at]as.itb.ac.id Abstract Interstellar matter plays an important role in our Galaxy. It is an ingredient to form stars, but it can also change the apparent properties of stars and other astronomical objects. Therefore, it is important to understand the distribution of the ISM in the Galaxy. Although ISM is concentrated within the galactic disk, at high galactic latitude, we can also find a smaller amount of ISM as part of shell-like structures which are known as ^loop^. Efforts to determine the distance of the loop structures have been carried out, but mostly for the North Galactic Spur or North Polar Spur (NPS). The distance of these structures is under debate: is it a local or distant Galactic structure? In this work, we aim at determining the distance of Loop I structure at the southern galactic latitude by using high-resolution spectroscopic data from ESO-HARPS and stellar parallaxes from GAIA EDR3. The interstellar tracers are NaI and CaII lines which are recorded in the reddened stellar spectra. Stellar parallaxes of the target stars are used to constrain the distance of the ISM. Our results favor that the Loop I is a local structure (around 80 pc from the Sun). Keywords: interstellar matter (ISM), Loop I, NPS, southern galactic latitude, spectroscopy Share Link | Plain Format | Corresponding Author (Ilham Maulana)

111	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-323
COMPARATIVE STUDY OF NATURAL BACKGROUND RADIATION BETWEEN MAMUJU REGENCY, WEST SULAWESI, AND WEST JAVA Zulfahmi1, Sidik Permana1,2,3,4, Adi R.A.Abdullah2, Imam Ghazali Y3, Ismail Humolongo4, Haryo Seno5 1Master Program in Physics of Teaching, Bandung Institute of Technology, Jl. Ganesha No. 10, Bandung, Indonesia 2Doctoral Program in Nuclear Engineering, Bandung Institute of Technology, Jl. Ganesha No. 10, Bandung, Indonesia. 3Master Program in Physic, Bandung Institute of Technology, Jl. Ganesha No. 10, Bandung, Indonesia. 4Master Program in Nuclear Science and Engineering, Bandung Institute of Technology, Jl. Ganesha No. 10, Bandung, Indonesia. 5Indonesia^s National Research and Inovation Agency, Jl. Tamansari No. 71, Bandung, Indonesia. Abstract Some areas has unique of radiation level, caused by high density of building or deposit of radioactive minerals. Mamuju district is the area with High Natural Background Radiation (HNBR) despite the low density of population, while West Java possesing low level radiation is the area with the largest population in Indonesia. Measurements of dose level in these two areas were carried out for two weeks covering nine villages in Mamuju and nine districts in West Java. The method used is random sampling to collect data from one meter on surface, while the tool used was the Ludlum model 19 series 8 Analog Survey meter. The results of radiation measurements were 2.500 mSv/year from 180 datas in Mamuju district and 0.2323 mSv/year in 103 datas in West Java. The big difference between the two is due to the presence of radioactive element-carrying minerals in Mamuju district, while in West Java areas there are no radioactive elements mineralization. Keywords: HNBR, surveymeter, dose rate, Mamuju, West Java. Share Link | Plain Format | Corresponding Author (Zulfahmi )

112	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-68
Light Pollution Measurement and Source Identification Premana W. Premadi(1,2), Vita I. Khikmah(1), Muhammad Yusuf(2), Dhani Herdiwijaya(1), and Sausan K. Haida 1. Astronomy Study Program, FMIPA, Institut Teknologi Bandung 2. Bosscha Observatory, FMIPA, Institut Teknologi Bandung Abstract Despite the claim that light pollution is the easiest to control, it is noticeably worsening worldwide as human population increases. The failure arises from the complication in identifying the main source of the light pollution and therefore in constructing an effective regulation on artificial lighting. We report a preliminary result of our study that aims at a light pollution profile over the years of each region that would guide the construction of a regulation that would systematically prevent light pollution. We conduct two independent studies to identify the various possible source of light pollution. The first one uses demographic data of the greater Bandung area and discovers that residential lights contribute much less than lights from business area, commercial attributes, and streetlights. The second study uses satellite data before, during, and after the Covid-19 epidemic lockdown period over Indonesia. We find that large cities show significant reduction in light pollution as many people worked from home, whereas rural areas show a slight increase or not at all. This result confirms that residential area contributes little to the worsening of light pollution, and that the primary source is pointed at human activities. To be precise: where and how human uses artificial light: commercial and industrial area, high rise offices, and ground transportation (automobiles and streetlight). A follow up study that combines satellite data and on-site ground data using Sky Quality Meter (SQM) is underway with the objective of identifying specific lighting particularly polluting astronomy sky. The correlation between the two types of data could later be used to have better guess of ground data when it is not available. Keywords: light pollution Share Link | Plain Format | Corresponding Author (Premana Premadi)

113	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-334
Atmospheric Extinction Measurement Using Narrowband Filter at ITERA Lampung Astronomical Observatory Rovanni Holly Setiawan (a*), Renza Alvionzo Barends (a), Yaniriang Fau (a), Gusti Ayu Nopia Lestari (a), Loria Oktaviane (a), Titania Jenny Amar Wulan Sari (a), Raihan Arsy (a), Aditya Abdillah Yusuf (b), Adhitya Oktaviandra (b), Izatul Hafizah (b), Hendra Agus Prastyo (a, b) a) Department of Atmospheric and Planetary Sciences, Sumatera Institute of Technology, Jalan Terusan Ryacudu, Lampung Selatan 35365, Indonesia *rovanni.119290057[at]student.itera.ac.id b) ITERA Lampung Astronomical Observatory, Jalan Terusan Ryacudu, Lampung Selatan 35365, Indonesia Abstract The atmosphere plays an essential role in sustaining life. On the other hand, it is also detrimental to astronomers. We have performed experiments to collect photometric data on some nebulas so that the influence of the atmosphere on the image results is substantial. Taking into account the physical parameters of the atmosphere is also the basis for measuring the feasibility of observation sites. As for some of the objects we have chosen- namely, Veil Nebula uses OIII filter, while Eagle Nebula uses H-Alpha and SII filters. From the observations, the extinction coefficient values varied the results for each filter. The measurement results of the extinction coefficient on the OIII filter, according to the observation of 5 stars, are 1.189- 1.171- 1.105- 1.146- and 1.082. Then, according to the observations of two standard stars, the extinction coefficient for H-Alpha filters are 1.231 and 1.22, while for SII filters are 0.98 and 0.893. Keywords: Atmospheric Extinction Measurement- Narrowband Filter- Extinction Coefficient Share Link | Plain Format | Corresponding Author (Rovanni Setiawan)

114	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-79
Crescent Moon Image Contrast Study Using DSLR Camera M. Hasan Faadillah (a*), Mahasena Putra (a,b) a) Astronomy Study Program, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Indonesia *faadillahmhasan[at]gmail.com b) Bosscha Observatory, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Indonesia Abstract Observation of new moon (young crescent) is almost always related to determination of the beginning months in the Hijri calendar. Observation/sighting of the new moon has gained much interest from various groups using instruments that are easy to obtain and widely available on the market. The use of portable telescope and DSLR camera is one the preferred configuration. Observations of new moon are usually carried out around twilight, where the moon is still relatively young, has a very weak light compared to the background sky (close to the Sun). Theoretical models of the visibility of celestial bodies, including Moon, around twilight had been developed by some authors. These open opportunities to study the contrast of crescent moon image, and put some constraints on models using the increasing amount of data. In this study, an alternative method for processing crescent moon images, obtained using DSLR camera (in Red, Green, and Blue channel), to estimate the brightness of the Moon and the background sky is presented. These two brightnesses are then used to determine the young crescent contrast, following a specific definition. The contrast values (\(C_{obs}\)) are compared to a theoretical model \(C=C(h_{\odot},\epsilon,h_{Moon})\), where \(h_{\odot}\), \(\epsilon\), and \(h_{Moon}\) are altitude of the Sun, elongation, and altitude of the Moon. Keywords: Contrast- DSLR camera- Hilal- Image processing- New moon crescent Share Link | Plain Format | Corresponding Author (M. Hasan Faadillah)

115	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-337
Instrumental Characteristics of ZWO ASI 533MM Pro CMOS Camera for Astronomy Research Renza Alvionzo Barends (a*), Rovanni Holly Setiawan (a), Yaniriang Fau (a), Gusti Ayu Nopia Lestari (a), Loria Oktaviane (a), Titania Jenny Amar Wulan Sari (a), Raihan Arsy (a), Aditya Abdillah Yusuf (b), Adhitya Oktaviandra (b), Izatul Hafizah (b), Hendra Agus Prastyo (a, b) a) Department of Atmospheric and Planetary Sciences, Sumatera Institute of Technology, Jalan Terusan Ryacudu, Lampung Selatan 35365, Indonesia *renza.119290063[at]student.itera.ac.id b) ITERA Lampung Astronomical Observatory, Jalan Terusan Ryacudu, Lampung Selatan 35365, Indonesia Abstract The character of the instruments used in the observation can affect the data obtained and further data processing. This study presents the instrumental characterization of the ZWO ASI 533MM Pro CMOS camera from bias, dark, and flat calibration images on BVRI filters. After taking flat image data, we found that the image was over-exposed on filters B, V, R, and I. The image on filter B was overexposed when the exposure time was 0.7 seconds, filter V when the exposure time was 0.35 seconds, filter R when the exposure time was 0.6 seconds and filter I when the exposure time was 28 seconds. From bias image data taken with 32 microseconds exposure time, obtained an average value of 397.7 ADU, a median value of 398 ADU, and a standard deviation of 2.3. Keywords: BVRI Filters- Calibration Images- Instrumental Characterization Share Link | Plain Format | Corresponding Author (Renza Alvionzo Barends)

116	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-82
Analysis Effects of Overshooting and Rotation Parameters in Intermediate-Mass Stars Defira Ramadia, Aprilia Institut Teknologi Bandung Abstract Stars undergo evolution during their lifetime, from protostars to white dwarfs. During this process, many parameters affect the evolution of stars, including overshooting and rotation. Adding variations in overshooting and rotation parameters to stellar evolution will result in different evolutionary tracks. The addition of overshooting and rotational effects has a similar effect on global star parameters, both processes resulting in increased luminosity and extended main sequence lifetimes. Overshooting and rotation affect the evolutionary path of intermediate mass stars, especially in the length of the blue loop line, which increases in the RGB phase. The addition of the overshooting and rotation also affects the luminosity, mass changes, interior composition, and age of the star. Using Linux-based MESA with the release series r12778, stellar evolution calculation will be carried out to review the effect of overshooting and rotation on the evolution of intermediate-mass stars with defined parameters. Keywords: Stellar Evolution - Overshooting - Rotation - MESA Share Link | Plain Format | Corresponding Author (Defira Ramadia)

117	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-86
Investigation the Impact of Equatorial-Rossby Waves on Extreme Rainfall in Java, Indonesia Mochamad Khoirul Rifai(a)(b), Eny Latifah(a*), Hari Wisodo(a), and Cahyo Aji Hapsoro(a) (a) Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Jl. Semarang 5, Malang, 65145, Indonesia (b) Junior High School of Darul Faqih Malang Indonesia, Jl. Gapura 197, Malang, 65158, Indonesia *Corresponding Author: eny.latifah.fmipa[at]um.ac.id Abstract Climate change has posed an urgent threat not only to the present generation but also to future generations. Even though climate change shows a very complex scheme, the pattern of change can still be observed and predicted. One of the changes that arise is the occurrence of fluctuations in rainfall to extreme rain and changes in other meteorological conditions. In this study, we conducted an in-depth investigation of the impact of Equatorial-Rossby (ER) waves on extreme rainfall in the region of Java Island, Indonesia. Based on an extensive station database (2000 to 2019) and the gridded Asian Precipitation-Highly Resolved Observational Data Integration Toward Evaluation of Water Resources (APHRODITE) product (2000 to 2019), we show that severe weather associated with extreme rainfall extremes in Java during the rainy season can also be attributed to ER waves. Evidence is presented that Equatorial Rossby (ER) waves significantly modulate daily rainfall extremes over Java Island. The convectively active (suppressed) phases of ER waves increase the probability of extreme rainfall by up to 45%, while the suppressed phases decrease this by up to 28%. In addition, the analysis of multiple wave events indicates that the ER waves^ positive (negative) interference leads to an amplification (suppression) of extreme rainfall probability. Overall, the results suggest that ER waves can provide an essential source of predictability for extreme rainfall events over Java Island. Keywords: Climate change- Extreme rainfall- ER waves- APHRODITE- Java Island. Share Link | Plain Format | Corresponding Author (Mochamad Khoirul Rifai)

118	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-87
Physical Properties of WR 90 (HD 156385) Based on Spectroscopic Study Bakuh Danang Setyo Budi (1,2), Hakim Luthfi Malasan (1,2,3,4*) 1) Department of Astronomy, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia 2) Bosscha Observatory, Institut Teknologi Bandung, Jalan Peneropongan Bintang, Bandung Barat 40391, Indonesia 3) Department of Atmospheric and Planetary Sciences, Institut Teknologi Sumatera, Lampung 35365, Indonesia 4) ITERA Astronomical Observatory (IAO), Institut Teknologi Sumatera, Lampung 35365, Indonesia *Email: malasan[at]itb.ac.id Abstract Wolf-Rayet star is one of the astronomical objects that have an emission line on its spectrum that exhibits unusual abundance of helium, nitrogen,carbon, and oxygen elements when compared to the spectrum of other stars in general. In this work, observation of WR 90 (HD 156385) was conducted using a low-resolution spectrograph NEO-R1000 (\(R\sim\)1000) at GAO-ITB RTS (27.94 cm,F/10.0), Bosscha Observatory. Determination of stellar parameters has been implemented using two different methods: The first method derives an estimation of effective temperature and radius using the blackbody continuum model approximation, second method to estimates stellar temperature, radius, and luminosity using PoWR (The Postdam Wolf-Rayet) spectrum grid model. Furthermore, asymptotic terminal velocity was derived from the gaussian decomposition of optical spectrum emission line and the P-Cygni profile analysis of the high-resolution IUE UV spectrum, the mass loss rate of Wolf-Rayet star has been determined. The data used in both methods are low- and high-resolution ultraviolet spectra retrieved from IUE (International Ultraviolet Explorer) archival and optical spectrum of our observations. The obtained results are compared with observations that have been made before. Keywords: Wolf-Rayet star, Physical Parameter, Blackbody Fitting, The Potsdam Wolf-Rayet Models (PoWR), Terminal Velocity, P-Cygni Analysis Share Link | Plain Format | Corresponding Author (Bakuh Danang Setyo Budi)

119	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-90
Identification of Worst Time on Determining Qibla Direction with Solar Azimuth M. Ihtirozun Ni^am (a), Ahmad Syifaul Anam (a) a) Universitas Islam Negeri Walisongo Semarang Jalan Prof. Hamka (Kampus III), Ngaliyan, Kota Semarang 50185, Indonesia *ihtirozun_n[at]walisongo.ac.id Abstract Qibla determination besides requiring fiqh as a basis for its legitimacy, also requires science to implement the concept. So far, the determination of Qibla direction has depended on the Sun as an accurate reference for direction. The daily apparent motion of the Sun makes the Sun^s position in the horizon coordinate system, both its altitude and azimuth values also change. This change will affect the selection of times that should be avoided when determining the Qibla direction. This article aims to identify the worst time to determine Qibla direction. The parameter used is when the azimuth of the Sun changes significantly within 1 minute. This is important to know because the average Qibla determination process can take up to 10 minutes or even more. Meanwhile, at certain times, the change in Qibla azimuth every 1 minute can reach 1 degree. So it is along these times, the Qibla determination can be inaccurate. The method used in this study is exploratory where the author conducted an experiment to calculate the change in the azimuth of the Sun in 1 day on the date the Sun is at the vernal equinox, autumnal euinox, winter solstice and summer solstice at 1 hour intervals, then it is eliminated and recalculated the largest azimuth change within 1 minute intervals. With the calculations performed, it is found that the Sun has a significant azimuth change (> 10 per minute) When the absolute value of: { ( WP + e + BT/15 - TZ) - 12 } x 15 < 150 where WP is Time for determining qibla, e is equation of time, BT is the Longitude, and TZ is Time Zone. In other words, it can be stated that the worst time in determining the Qibla with the azimuth of the Sun is 1 hour before and after the Sun is at its culmination point. Keywords: Worst Time- Qibla Direction- Solar Azimuth Share Link | Plain Format | Corresponding Author (M. Ihtirozun Niam)

120	EARTH, ATMOSPHERIC, AND SPACE SCIENCE	ABS-348
Slit Grating and its Use in Visual Double Stars Observation Satrio Fatkhusalma (1,2*), Mochamad Irfan (2), Hakim Luthfi Malasan (1,2,3,4) 1) Astronomy Division, Institut Teknologi Bandung, Bandung 40312, Indonesia 2) Bosscha Observatory, Institut Teknologi Bandung, Bandung 40312, Indonesia 3) Department of Atmospheric and Planetary Sciences, Institut Teknologi Sumatera, Lampung 35365, Indonesia 4) ITERA Astronomical Observatory, Institut Teknologi Sumatera, Lampung 35365, Indonesia Abstract Visual double star is a type of double stars in which studies about the orbits of the system has interesting value. The visual double star^s orbit became harder to analyse if the pair has large difference in magnitude and small separation angle. There are many methods which can be used to facilitate the analysis of the centroid of its orbit. One of those methods is by using double star grating. Double star grating can be used for visual double star that has large difference in magnitude and small separation angle. This grating works in similar principle as diffraction, in which it scattered incoming light and reduced the light^s intensity, so the double star^s orbit centroid can be easily determined. In this work, the visual double star observation of WDS 19387-1009 (STF2545AB) and WDS 22525-3253 (HJ5367) has been taken by using Zeiss 60 cm Double Refractor at Boscha Observatory with the double star grating that was placed around 20 cm before Zeiss 60 cm Double Refractor objective lens. Standard image reduction was done by using IRAF, so that clean images were obtained. The centroid of each double star will be analysed using PSF (Point Spread Function) fitting. The smallest error from PSF fitting will be chosen. The final data from this work (position angle and separation angle) will be uploaded to WDS catalogue for further analysis. Keywords: Visual Double Stars, Centroid Determination, PSF Fitting, Transmission Grating Share Link | Plain Format | Corresponding Author (Satrio Fatkhusalma)

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