• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.117-124
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• 2005

We plan to install the polarimetric optics in the AGU(acqusition and guiding unit) of the 1.8 m telescope at the BOAO(Bohyunsan Optical Astronomy Observatory). With this, the spectropolarimetric observations with the resolution of 45,000 and 60,000 in 4,000 to $8,000{\AA}$ ange could be done by the BOES(BOao Echelle Spectrograph). If we use the precision radial velocity measurement capability of the BOES, the accuracy of the magnetic field intensity measurements with this new BOES stokesmeter will be much increased. We present here the design concept of the BOES stokesmeter. Some details on the optics, mechanical parts, fiber parts and the lab test procedures of this stokesmeter are explained.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.47-54
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• 2004

We present the detailed description on the fiber techniques adopted in the BOES: the design concepts and manufacturing of the v grooves, the procedures of the fiber polishing, adhering of the fibers to the v grooves, and the axis alignment of the fiber input and exit. The high efficiency and throughput of the BOES imply that the adopted fiber arts and the other optical components were well designed and properly treated. We learned that the relatively low efficiency of the 80 micron fiber comparing with the 200 and 300 micron fibers comes from the seeing and the guiding effects not from the poor fiber handling.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.65-70
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• 2004

An imaging spectrograph concept optimized for extended far-ultraviolet emission sources is presented. Although the design was originally developed for FIMS aboard the first Korean science satellite STSAT-l launched on September 27, 2003, no rigorous theoretical background of the spectrograph design has been published. The spectrograph design employs an off-axis parabolic cylinder mirror in front of a slit that guides lights to a diffraction grating. The concave grating provides moderate spatial resolution over a large field of view. This mapping capability is absent in most astronomical instruments but is crucial to the understanding of the nature of a variety of astrophysical phenomena. The aberration theory presented in this paper can be extended to holographic gratings in order to improve the spatial as well as the spectral resolutions.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.63.1-63.1
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• 2010

Over its 30-year lifetime, UKIRT has been the world's leading telescope devoted exclusively to observations in the infrared. Its outstanding success over this period is attributable to a number of factors, foremost among which are the size (3.6m) and high quality of the mirror, the excellent site at the summit of Mauna Kea, and the deployment of unique, world-beating instrumentation. In recent years, as the UK has re-directed its investment in astronomical facilities towards ESO, UKIRT has focussed on wide-field imaging in the near infrared, and we are currently conducting a definitive programme known as the UKIRT Infrared Deep Sky Survey (UKIDSS). In this presentation I will describe UKIRT's current capabilities, its evolving operation, opportunities for Korean participation, and possibilities for its future development.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.185-191
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• 2004

We have been developing a solar observing system based on a fast CCD camera 1M30P made by the DALSA company. Here we examine and present the characteristics and performance of the camera. For this we have analyzed a number of images of a flat wall illuminated by a constant light source. As a result we found that in the default operating mode 1) the mean bias level is 49 ADU/pix, 2) the mean dark current is about 8 ADU /s/pix, 3) the readout noise is 1.3 ADU, and 4) the gain is about 42 electrons/ ADU. The CCD detector is found to have a linearity with a deviation smaller than $6\%$, and a uniform sensitivity better than $1\%$. These parameters will be used as basic inputs in the analysis of data to be taken by the camera.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.125.1-125.1
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• 2011

After a short description of the observatory, this presentation will highlight some of the most recent scientific achievements based on CFHT observations and how they benefit from the current instrumentation and novel observing modes proposed to the CFHT users. We will then move to the mid-term future with the development of new spectroscopic capabilities (visible wide-field FTS or near-IR spectro-polarimetry) and the study of a novel wide-field imager in the visible using Ground-Layer AO to provide unprecedented image quality on a large field of view. As an option for the long-term future, the concept of a next generation 10-m class telescope to replace the current CFHT 3.6-m will be described. An emphasis will be given on how CFHT is slowly morphing into an Asia-Pacific Rim observatory and on the role the Korean community could play in such an endeavor, from immediate access to first-class astronomical data to partnering with other nations in exciting developments.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.675-677
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• 2015

A data simulator and reduction package for the Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) has been developed. Since data reduction for the Integral Field Spectrograph (IFS) requires complicated procedures due to the complex nature of the integral spectrograph, common reduction procedures are usually not directly applicable for such an instrument. Therefore, the development of an optimized package for the DOTIFS is required. The data simulator observes artificial object and simulates CCD images for the instrument considering various effects; e.g. atmosphere, sky background, transmission, spectrograph optics aberration, and detector noise. The data reduction package has been developed based on the outcomes from the DOTIFS data simulator. The reduction package includes the entire processes for the reduction; pre-processing, flat-fielding, and sky subtraction. It generates 3D data cubes as a final product, which users can use for science directly.

• Publications of The Korean Astronomical Society
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• v.37 no.3
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• pp.35-47
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• 2022

This study investigated the stone Angbu-ilgu (scaphe sundial) of the Korea Meteorological Administration (KMA) and the Seoul Museum of History (SMH). Since the first Angbu-ilgu was produced in Korea in 1434 (the year of the reign of King Sejong), Angbu-ilgu has been reproduced with various materials. The upper surface of these two stone Angbu-ilgus symbolizes the horizon. On the hemisphere concave at the center of the horizon, the South Pole, the time line, and the season line are engraved. On the horizon of both the KMA and SMH Angbu-ilgus, the schematic, typeface, and composition of the inscription completely coincide with each other. In this study, it was estimated that the appearance of the KMA Angbu-ilgu, which was damaged at some point previously at least once, was similar to that of the SMH Angbu-ilgu, and this means that it is superficially similar with Treasure No 840, the stone horizontal sundial. In the concave hemisphere of both the stone Angbu-ilgus of the KMA and SMH, there are hour lines and 24 solar-term lines (13 line), and there is an intersection point where these lines meet the horizon, respectively. It can be verified that these intersections of these two Angbu-ilgus can be calculated as having a latitude of +37°39'15". The hour lines of the two stone Angbu-ilgus show that they were made after about 1900.

• Publications of The Korean Astronomical Society
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• v.38 no.1
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• pp.1-12
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• 2023

Numerous Sundials were fabricated during the reign of King Sejong of the Joseon Dynasty. One among them is Jeongnam-Ilgu (the Fixing-South Sundial), where the time can be measured after setting up the suitable meridian line without a compass. We reconstructed the new Jeongnam-Ilgu model based on the records of 'Description of Making the Royal Observatory Ganui (簡儀臺記)' in the Veritable Record of King Sejong. Jeongnam-Ilgu has a summer solstice half-ring under a horizontal ring which is fixed to two pillars in the north and south, and in which a declination ring rotates around the polar axis. In our model, the polar axis matches the altitude of Hanyang (that is Seoul). There are two merits if the model is designed to install the polar axis in the way that enters both the north and south poles and rotates in them: One is that it is possible to fix the polar axis to the declination ring together with the cross-strut. The other is that a twig for hanging weights can be protruded on the North Pole. The declination ring is supposed to be 178 mm in diameter and is carved on the scale of the celestial-circumference degrees on the ring's surface, where a degree scale can be divided into four equal parts through the diagonal lines. In addition, the time's graduation that is drawn on the summer solstice half-ring makes it possible to measure the daytime throughout the year. An observational property of Jeongnam-Ilgu is that a solar image can be obtained using a pin-hole. The position cast by the solar image between hour circles makes a time measurement. We hope our study will contribute to the restoration of Jeongnam-Ilgu.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.73-75
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• 2005

The latest scientific highlights obtained with the Subaru telescope are given together with its current status and on-going instrumentation. We have been successfully operating the telescope and 8 observatory instruments (including an adaptive optics system) since January 1999, when the first light was accomplished. Open-use of Subaru began in December 2000. Subaru has a unique capability of its prime focus among other 8-10 meter class telescopes and has an excellent imaging performance as a result of its sophisticated active optics combined with the high stability of the sky at Mauna Kea. Scientific highlights are given on the discoveries of the most distant galaxies, spiral structure on a protoplanetary disk around AB Aur, and planetesimal belts in the debris disk around $\beta$ Pic. Brief summaries are given for three new instruments: the Multi-Object Infrared Camera and Spectrograph (MOIRCS), 188 element adaptive optics system, and Fiber Multi-Object Spectrograph (FMOS)