• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.18-18
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• 1992

Spectroscopic CCD observations were carried out for V 1119 Cygni and the spectrum inthe visual region is analysed relative to the SLln with a line-blanketed convective modelatmosphere. Adopted atmospheric parameters are : an effective temperature ( Teff) =7000 K, a surface gravity log g = 3.4. Although our result is dependent onmicroturbulent velocity and damping constant, it was found that Mg in V1719 Cygni isnearly solar, or underabundant by 0.2 to 0.3 dex according to the analysis of5172.684A Mg I line which is relatively free from blending. This is inconsistentwith the previous photometric result wh(:re V1719 Cygni was known as anabnormally metal rich variable.

• Publications of The Korean Astronomical Society
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• v.25 no.2
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• pp.31-49
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• 2010

Next to Paper I (Jeon 2009a), time-series BV CCD images of the open cluster M38 were taken for 4 nights on December, 2009. The observations have been carried out for total 27 nights. In addition to the 20 variable stars in the Paper I, the discovery of 44 new variable stars has been presented in this paper: $6{\delta}$ Scuti stars, $2{\gamma}$ Doradus stars, 18 eclipsing binaries and 18 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the ${\delta}$ Scuti and ${\gamma}$ Doradus stars, multi-frequency analysis was performed using the Discrete Fourier Transform and linear least-square fitting. The period search for the eclipsing binaries and the semi-long periodic and/or slow irregular type variable stars was performed by phase fitting method. As a result, the periods for 23 variable stars among the 44 ones were defined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1570-1577
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• 2002

In order to investigate the characteristics of two-phase slug flow, an electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under single-phase flow was $\pm$ 2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble. Besides, it is an easier and cheaper method for measuring mean film velocity than others such as photochromic dye activation method or particle image velocimetry.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.27-31
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• 2004

Through time-series CCD photometry using a 155mm refractor, we found a new $\delta$ Scuti type variable star, HD 235428, near a known bright $\delta$ Scuti type star, DQ Cep. We performed follow-up observations using a 61cm telescope at Sobaeksan Optical Astronomy Observatory. Four frequencies have been derived by multiple-frequency analysis, which are 15.804, 5.498, 15.351 and 24.516cycle $day^{-1}$, respectively. V-amplitude of HD 235428 is ${\Delta} V$ = 0.026.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.33-37
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• 2004

Through time-series CCD photometry using a 130mm refractor of Busan Science Academy, we found a new $\delta$ Scuti type variable star, esc 03665-00576. We performed following observations using a 1.8m telescope of Bohyunsan Optical Astronomy Observatory. Three frequencies have been derived by multiple-frequency analysis, which are 10.968, 7.156 and 15.182cycle $day^{-1}$, respectively. V-amplitude of esc 03665-00576 is ${\Delta}V$= 0.04.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.179-184
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• 2004

We have developed a wide-field imaging camera system, called WICZO, to monitor light of the night sky over extended period. Such monitoring is necessary for studying the morphology of interplanetary dust cloud and also the time and spatial variations of airglow emission. The system consists of an electric cooler a CCD camera with $60\%$ quantum efficiency at 500nm, and a fish-eye lens with $180^{\circ}$ field of view. Wide field imaging is highly desired in light of the night sky observations in general, because the zodiacal light and the airglow emission extend over the entire sky. This paper illustrates the design of WICZO, reports the result of its laboratory performance test, and presents the first night sky image, which was taken, under collaboration with Byulmaro Observatory, on top of Mt. Bongrae at Yongweol in January, 2004.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.103.2-103.2
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• 2011

We measure the degree of polarization of the lunar regolith to map the distributions of the age and the particle size. We use a 12cm refracting telescope with a 2k-square pixel color CCD (R band) and a polarization filter. The angular resolution obtained is 3.02 km/pixel. Our goal is to obtain a map of the lunar particle size distribution on the lunar regolith and then that of the age distribution. Polarization of the light scattered by lunar surface contains information on their mean particle size. The mean particle size of the lunar surface has been decreased by continued micro-meteoroid impact over a long period. One can estimate the age of the lunar surface if the mean particle size is known. Particle sizes can be measured through observations of polarization because the mean particle size is related to the maximum polarization and albedo. The age and the particle size of the lunar regolith can give vital information for the future lunar exploration.

• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.141-149
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• 2007

Preliminary time-series observations for short-period variability survey (SPVS) were carried out using a 155mm refractor and a $2k{\times}3k$ CCD camera at Bohyunsan Optical Astronomy Observatory. We found 21 new variable stars in the $90'{\times}60'$ test field region : 9 eclipsing binary stars, $5{\delta}$ Scuti type stars, a ${\gamma}$ Doradus type star, and 6 long period variables. The observing field center is R.A. $05^h\;00^m\;00^s$, DEC. $50^{\circ}\;00'\;00"$ (J2000.0). The period and amplitude ranges for the short-period variables, i.e., ${\delta}$ Scuti stars, were 0.052day - 0.107day and 0.012mag - 0.064mag, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.63.3-63.3
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• 2016

NYSC 1m telescope is completely assembled now, and equipped with FLI PL-16803 4k CCD and Shelyak eShel spectrograph (R~10,000) on optical system of f/8. From 12th Jan 2016, optical system alignment and test observations have been performed. We present the result of M35 photometric observation for the performance test of the 1m telescope. The photometric observation was carried out for the central part of M35 with the field of view, ${\sim}15^{\prime}.8{\times}15^{\prime}.8$. Standard transformation to the UBVI system was done by the photometric data of M35 in Sung and Bessell(1999).

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.683-685
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• 2015

A group of universities have come together with the aim of designing and developing Small Aperture Robotic Telescopes (SmART) for use by students to observe variable stars and transient follow-ups. The group is deliberating on the components of the robotic system; e.g. the telescope, the mount, the back-end camera, control software, and their integration keeping in mind the scientific objectives. The prototype might then be replicated by all the participating universities to provide round the clock observations from sites spread evenly in longitude across the globe. Progress made so far is reported in this paper.