• 제목/요약/키워드: astronomical instruments

검색결과 149건 처리시간 0.021초

DETECTION AND RESTORATION OF NON-RADIAL VARIATION OVER FULL-DISK SOLAR IMAGES

  • Yang, Yunfei;Lin, Jiaben;Feng, Song;Deng, Hui;Wang, Feng;Ji, Kaifan
    • 천문학회지
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    • 제46권5호
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    • pp.191-200
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    • 2013
  • Full-disk solar images are provided by many solar telescopes around the world. However, the observed images show Non-Radial Variation (NRV) over the disk. In this paper, we propose algorithms for detecting distortions and restoring these images. For detecting NRV, the cross-correlation coefficients matrix of radial profiles is calculated and the minimum value in the matrix is defined as the Index of Non-radial Variation (INV). This index has been utilized to evaluate the H images of GONG, and systemic variations of different instruments are obtained. For obtaining the NRV's image, a Multi-level Morphological Filter (MMF) is designed to eliminate structures produced by solar activities over the solar surface. Comparing with the median filter, the proposed filter is a better choice. The experimental results show that the effect of our automatic detection and restoration methods is significant for getting a flat and high contrast full-disk image. For investigating the effect of our method on solar features, structural similarity (SSIM) index is utilized. The high SSIM indices (close to 1) of solar features show that the details of the structures remain after NRV restoring.

Structure and Conceptual Design of a Water-Hammering-Type Honsang for Restoration

  • Lee, Yong-Sam;Kim, Sang-Hyuk
    • Journal of Astronomy and Space Sciences
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    • 제29권2호
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    • pp.221-232
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    • 2012
  • We analyzed the manufacturing procedure, specifications, repair history, and details of celestial movements of the water-hammering type $Honsang$ (celestial globe). Results from our study on the remaining $Honsangs$ in China and Japan and on the reconstruction models in Korea were applied to our conceptual design of the water-hammering type $Honsang$. A $Honui$ (armillary sphere) and $Honsang$ using the water-hammering method were manufactured in $Joseon$ in 1435 (the 17th year of King $Sejong$). $Jang$ $Yeong-Sil$ developed the $Honsang$ system based on the water-operation method of $Shui$ $y{\ddot{u}}n$ $i$ $hsiang$ $t'ai$ in China. Water-operation means driving water wheels using a water flow. The most important factor in this type of operation is the precision of the water clock and the control of the water wheel movement. The water-hammering type $Honsang$ in $Joseon$ probably adopted the $Cheonhyeong$ (天衡; oriental escapement device) system of $Shui$ $y{\ddot{u}}n$ $i$ $hsiang$ $t'ai$ in China and the overflow mechanism of $Jagyeongnu$ (striking clepsydra) in $Joseon$, etc. In addition to the $Cheonryun$ system, more gear instruments were needed to stage the rotation of the $Honsang$ globe and the sun's movement. In this study, the water-hammering mechanism is analyzed in the structure of a water clock, a water wheel, the $Cheonhyeong$ system, and the $Giryun$ system, as an organically working operation mechanism. We expect that this study will serve as an essential basis for studies on $Heumgyeonggaknu$, the water-operating astronomical clock, and other astronomical clocks in the middle and latter parts of the $Joseon$ dynasty.

Technical endeavor to minimize astronomical instruments in the Joseon dynasty

  • Mihn, Byeong-Hee;Lee, Ki-Won;Ahn, Young Sook;Lee, Yong Sam
    • 천문학회보
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    • 제39권1호
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    • pp.87-87
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    • 2014
  • 조선 전기 세종(世宗, 1418-1450)에 의해 천체관측기기와 천문역법을 개발하는 사업이 있었다. 이 때 조선의 천문대인 간의대가 건설되었고, 더불어 소간의, 일성정시의, 현주일구, 천평일구, 정남일구, 앙부일구 등 다수의 소형화된 천문의기가 개발되었다. 이보다 앞서 중국 원(元)왕조의 최신 관측기기였던 간의, 규표, 혼천의, 혼상 등을 제작하였는데, 이 과정에서 습득한 기술적 경험을 바탕으로 소형화된 천문의기 새롭게 발전시킨 것으로 보인다. 당시 천문의기를 구성하는 것에는 천구의 도수를 눈금으로 새긴 원형의 환(環)이나 구형의 혼(渾)이 있었다. 조선에서는 시헌력을 도입하기 전까지 천구의 도수(주천도수)를 365.25 등분하였고, 하루 12시진을 백각으로 나누었으며, 이를 각각 주천도분환과 백각환에 눈금을 새기었다. 당시에는 환의 둘레에 주천도수와 백각을 새기는 기술적인 어려움이 있었다. 이러한 제작 상의 문제를 해결하는 방법으로, 본 연구에서는 도수나 시각의 각거리를 일정한 길이의 단위로 설정하여 원주를 등분하였을 것으로 가정하였다. 즉 조선의 소형화된 천문의기는 주천도의 1도나 백각의 1각을 일정한 길이의 단위인 푼이나 치의 정수배로 하여 환의 둘레에 주천도수와 백각의 눈금을 새겼을 것으로 추정하였다. 만일 주천도의 1도 각거리를 1푼으로, 백각의 1각 각거리를 1푼으로 하는 표준 변환을 적용하면, 각각 환의 지름이 1.16치, 0.32치가 된다. 이러한 방법이 현존하는 일성정시의나 소간의의 세 종류의 환과 현주일구의 백각환의 특성과 잘 일치함을 보이고 있다. 이 연구의 결과는 향후 소형화된 천문의기의 구조적인 재원을 연구할 때나 출처가 불분명한 의기의 크기를 이해하는데 주요한 역할을 할 수 있을 것으로 기대한다.

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Curves on the Mother and Indices of the Rete Carved to Ryu Geum's Astrolabe

  • Mihn, Byeong-Hee;Kim, Sang Hyuk;Nam, Kyoung Uk;Lee, Ki-Won;Jeong, Seong Hee
    • 천문학회보
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    • 제43권2호
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    • pp.48.4-49
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    • 2018
  • We studyed an Korean astrolabe made by Ryu Geum (1741~1788), the late Joseon Confucian scholar. It has a diameter of 17 cm and a thickness of 6 mm and is now owned by Museum of Silhak. In the 1267 of the reign of Kublai Khan of Mogol Empire, Jamal al Din, an Ilkhanate astronomer, present an astrolabe to his emperor together with 6 astronomical instruments. In 1525, an astrolabe was first made in Korea by Lee, Sun (李純, ?~?), a Korean astronomer and royal official of Joseon Dynasty. He was referred to Gexiang xinshu, a Mongloian-Chinese book by Zhao, Youqin (1280-1345), an astronomer of Mongolian Empire. This astrolabe has not been left. In the mid-17th century, an astrolabe was introduced to Joseon again through Hungai tongxian tushuo (渾蓋 通憲圖設) edited by Chinese Mathematician Li Zhi-zao (李之藻, 1565~1630), that originated from Astrolabium (1593) of Christoph Clavius (1538-1612). It seems that Ryu refered to Hungai tongxian tushuo which affect to Hongae-tongheon-ui (渾蓋通憲儀) edited by Nam, Byeong-Cheol (南秉哲, 1817~1863). We analysis lots of circles on the mother and a set of index from the rete of of Ryu's astrolabe. We find that the accuracy of circles has about 0.2~0.4 mm in average if the latitude of this astrolabe is 38 degrees. 11 indices of the rete point bright stars of the northern and southern celestial hemisphere. Their tip's accuracies are about $2^{\circ}.9{\pm}3^{\circ}.2$ and $2^{\circ}.3{\pm}2^{\circ}.8$ on right ascension and declination of stars respectively.

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중등 교사의 과학 교수 효능감이 천문 수업에 미치는 영향 : 근거이론을 중심으로 (The Effect of Science Teaching Efficacy Belief of Secondary School Teachers on Astronomy Topics: Based on Grounded Theories)

  • 배성희;김형범
    • 한국콘텐츠학회논문지
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    • 제16권3호
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    • pp.607-616
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    • 2016
  • 이 연구의 목적은 중등 과학 교사의 과학 교수 효능감에 따라서 천문 수업에서 나타나는 수업 반응은 어떠한지를 알아보았다. 2009개정 과학과 교육과정 내용체계 중 '태양계'와 '외권과 우주개발'을 담당하는 중학교 과학교사들을 대상으로 무선 표집하여 29부의 과학 교수 효능감에 관한 질문지를 배부하였으며, 이 중 응답이 완결된 27부를 연구 자료로 채택하였다. 또한 질문지로부터 나온 총점을 빈도 분석하여 상위 및 하위 5%를 본 연구의 연구대상으로 선정하였으며, 자료 수집을 위해 준참여관찰, 녹음, 반구조화된 면담 등의 방법을 사용하였다. 그 결과는 다음과 같다. 첫째, 효능감이 높은 과학 교사의 수업에서는 천문 분야와 관련된 전문적인 지식에 대한 접근성이 뛰어나고 교과 내용학 지식이 매우 높았다. 둘째, 효능감이 낮은 교사가 교사 위주의 수업을 지향하고 있는 반면, 과학 교수 효능감이 높은 교사는 학습자 위주의 수업과 이에 맞는 수업전략이 마련되어 있었다. 셋째, 과학 교수 효능감이 높은 교사는 천문연구회를 통한 과학지식뿐만 아니라 다양한 기구를 활용할 수 있는 아이디어를 제공받고 있었다. 따라서 천문수업에 대한 자신감과 교과 내용학 지식을 통한 수업전략 뿐만 아니라 천문관측과 같은 수업관련 활동이 과학 교수 효능감을 유의미하게 예측해 주는 중요 변인이었다.

MINERVA: SMALL PLANETS FROM SMALL TELESCOPES

  • WITTENMYER, ROBERT A.;JOHNSON, JOHN ASHER;WRIGHT, JASON;MCCRADY, NATE;SWIFT, JONATHAN;BOTTOM, MICHAEL;PLAVCHAN, PETER;RIDDLE, REED;MUIRHEAD, PHILIP S.;HERZIG, ERICH;MYLES, JUSTIN;BLAKE, CULLEN H.;EASTMAN, JASON;BEATTY, THOMAS G.;LIN, BRIAN;ZHAO, MING;GARDNER, PAUL;FALCO, EMILIO;CRISWELL, STEPHEN;NAVA, CHANTANELLE;ROBINSON, CONNOR;HEDRICK, RICHARD;IVARSEN, KEVIN;HJELSTROM, ANNIE;VERA, JON DE;SZENTGYORGYI, ANDREW
    • 천문학논총
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    • 제30권2호
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    • pp.665-669
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    • 2015
  • The Kepler mission has shown that small planets are extremely common. It is likely that nearly every star in the sky hosts at least one rocky planet. We just need to look hard enough-but this requires vast amounts of telescope time. MINERVA (MINiature Exoplanet Radial Velocity Array) is a dedicated exoplanet observatory with the primary goal of discovering rocky, Earth-like planets orbiting in the habitable zone of bright, nearby stars. The MINERVA team is a collaboration among UNSW Australia, Harvard-Smithsonian Center for Astrophysics, Penn State University, University of Montana, and the California Institute of Technology. The four-telescope MINERVA array will be sited at the F.L. Whipple Observatory on Mt Hopkins in Arizona, USA. Full science operations will begin in mid-2015 with all four telescopes and a stabilised spectrograph capable of high-precision Doppler velocity measurements. We will observe ~100 of the nearest, brightest, Sun-like stars every night for at least five years. Detailed simulations of the target list and survey strategy lead us to expect $15{\pm}4$ new low-mass planets.

Polarimetry of solar system small bodies using the Seoul National University 61cm telescope and TRIPOL

  • Jin, Sunho;Ishiguro, Masateru;Kwon, Yuna Grace;Geem, Jooyeon;Bach, Yoonsoo P.;Seo, Jinguk;Sasago, Hiroshi;Sato, Shuji
    • 천문학회보
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    • 제44권1호
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    • pp.64.2-64.2
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    • 2019
  • It is known that lights scattered by comets and asteroids are partially polarized. From polarimetric observations of those objects, we can investigate physical properties, such as albedos, sizes of cometary dust particles and regolith of asteroids. Since the polarization degrees of those objects highly depend on their phase angles (Sun-object-observer's angles), long-term monitoring observations are required. Moreover, comets show unforeseeable activations (i.e., outbursts) which need follow-up observations to understand the mechanism. In order to realize such monitoring and transient observations, we installed the Triple-Range Imager and POLarimeter (TRIPOL) on the 61cm telescope of Seoul National University (Hereafter, SNU) Gwanak campus. With this combination, we can obtain g', r', i' bands photopolarimetric images simultaneously with $8.0^{\prime}{\times}8.0^{\prime}$ field of view and pixel resolution of 0.94" pixel-1. Here, we make a presentation regarding the photometric and polarimetric performances of TRIPOL on the SNU 61cm telescope. In addition, we introduce initial polarimetric results of asteroid and comets with the instruments. First, we determine the limiting magnitudes (defined as magnitudes for S/N=5) of $15.17{\pm}0.06$ (g'-band), $15.68{\pm}0.01$ (r'-band), $16.24{\pm}0.03$ (I'-band), respectively, with total 240-seconds exposure (four 60-seconds exposure images, each was taken at different rotation angle for the half-wave plate). Second, we found that the instrumental polarization is negligibly small, ($-0.32{\pm}0.04%$ in the g', $-0.36{\pm}0.05%$ in the r' and $-0.21{\pm}0.04%$ in the i'-bands), while the polarization efficiencies are large enough to maximize the performance (i.e., $97.52{\pm}0.03%$ in the g', $98.83{\pm}0.02%$ in the r' and $99.15{\pm}0.02%$ in the i'-bands). With the instruments, we made observations of three Jupiter-family comets, 21P/Giacobini-Zinner, 38P/Stephan-Oterma, and 46P/Wirtanen and plan to observe one near-Earth asteroid, (433) Eros, on a trial basis. Especially for comets, we discriminate signals from dust and gas to eliminate gas contamination, which are known to change observed degree of linear polarization, using multi-band images. We confirm that the phase angle dependency of these comets are consistent with previous observations, probably because polarimetric property of Jupiter-family comets are broadly homogeneous unlike asteroids. We will also describe future observation plans using TRIPOL and SNU 61cm telescope.

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한국천문연구원 Hα 태양전면관측시스템의 바닥고르기 연구 (FLAT-FIELDING FOR SOLAR FULL DISK Hα MONITORING SYSTEM OF KASI)

  • 박형민;김연한;봉수찬;박영득;조경석;장비호;최성환;나자경;이승민;채종철
    • 천문학논총
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    • 제23권2호
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    • pp.47-52
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    • 2008
  • We have performed the flat-fielding correction for the $H{\alpha}$ full-disk monitoring system of KASI (Korea Astronomy and Space Science Institute), which is installed in the Solar Flare Telescope (SOFT) at the top of Bohyun Mountain. For this, we used a new method developed by Chae (2004), to determine the flat pattern from a set of relatively shifted images. Using this method, we successfully obtained the flat pattern for $H{\alpha}$ full-disk observations and compared our result with the image observed in Catania Astrophysical Observatory. The method that we used in this study seems to be quite powerful to obtain the flat image for solar observations. In near future, we will apply this method for the flat-fielding correction of all solar imaging instruments in KASI.

TOWARD A NEXT GENERATION SOLAR CORONAGRAPH: DIAGNOSTIC CORONAGRAPH EXPERIMENT

  • Cho, Kyung-Suk;Yang, Heesu;Lee, Jae-Ok;Bong, Su-Chan;Kim, Jihun;Choi, Seonghwan;Park, Jongyeob;Cho, Kyuhyoun;Baek, Ji-Hye;Kim, Yeon-Han;Park, Young-Deuk
    • 천문학회지
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    • 제53권4호
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    • pp.87-98
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    • 2020
  • The Korea Astronomy and Space Science Institute (KASI) has been developing a next-generation coronagraph (NGC) in cooperation with NASA to measure the coronal electron density, temperature, and speed simultaneously, using four different optical filters around 400 nm. KASI organized an expedition to demonstrate the coronagraph measurement scheme and the instrumental technology during the 2017 total solar eclipse (TSE) across the USA. The observation site was in Jackson Hole, Wyoming, USA. We built an eclipse observation system, the Diagnostic Coronal Experiment (DICE), composed of two identical telescopes to improve the signal-to-noise ratio. The observation was conducted at four wavelengths and three linear polarization directions in the limited total eclipse time of about 140 seconds. We successfully obtained polarization data for the corona but we were not able to obtain information on the coronal electron temperature and speed due to the low signal-to-noise ratio of the optical system and strong emission from prominences located at the western limb. In this study, we report the development of DICE and the observation results from the eclipse expedition. TSE observation and analysis with our self-developed instrument showed that a coronagraph needs to be designed carefully to achieve its scientific purpose. We gained valuable experience for future follow-up NASA-KASI joint missions: the Balloon-borne Investigation of the Temperature and Speed of Electrons in the Corona (BITSE) and the COronal Diagnostic EXperiment (CODEX).

EVALUATION OF FAR-INFRARED BIB-TYPE GE DETECTORS FABRICATED WITH THE SURFACE-ACTIVATED WAFER BONDING TECHNOLOGY

  • Hanaoka, Misaki;Kaneda, Hidehiro;Oyabu, Shinki;Hattori, Yasuki;Tanaka, Kotomi;Ukai, Sota;Shichi, Kazuyuki;Wada, Takehiko;Suzuki, Toyoaki;Watanabe, Kentaroh;Nagase, Koichi;Baba, Shunsuke;Kochi, Chihiro
    • 천문학논총
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    • 제32권1호
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    • pp.351-353
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    • 2017
  • To realize large-format compact array detectors covering a wide far-infrared wavelength range up to 200 µm, we have been developing Blocked-Impurity-Band (BIB) type Ge detectors with the room-temperature surface-activated wafer bonding technology provided by Mitsubishi Heavy Industries. We fabricated various types of $p^+-i$ junction devices which possessed a BIB-type structure, and evaluated their spectral response curves using a Fourier transform spectrometer. From the Hall effect measurement, we also obtained the physical characteristics of the $p^+$ layers which constituted the $p^+-i$ junction devices. The overall result of our measurement shows that the $p^+-i$ junction devices have a promising applicability as a new far-infrared detector to cover a wavelength range of $100-200{\mu}m$.