• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.34-35
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• 2002

Large-screen projectors for video applications and computer monitors are convenient instruments for conference presentations as well as for TV use at home. Recently, CRT and LCD projectors have achieved higher resolutions and luminance in the projection TV The large surface of the CRT compared to the LCD allows a great number of pixels to be displayed, while simultaneously providing maximum brightness of the final picture. (omitted)

• Journal of The Korean Astronomical Society
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• v.35 no.2
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• pp.87-95
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• 2002

We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18' $\times$ 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V $\approx$ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv $\approx$ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (${\phi}(m){\propto} m^{-(1+x)},x = 1.35$).

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.91-96
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• 2006

We use near-infrared observations of eight selected Galactic globular clusters to estimate their distances by comparing the observed and theoretically predicted K magnitudes of the red giant branch bumps and tips. The K magnitude levels of the RGB bump and tip have been measured from the luminosity function of the selected RGB stars in the clusters. Theoretical absolute $M_k$ magnitudes of the RGB bump and tip are taken from the Yonsei-Yale isochrones. Comparing the observed apparent K magnitude with the derived absolute $M_k$ magnitude, we calculate the distance moduli of the clusters. We discuss the dependency of the derived distance modulus on the cluster age and the uncertainty of the distance measurement from the near-infrared photometry of the RGB bump and tip.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.79-80
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• 1996

We performed CCD surface photometry in B,V,R and I filters for three southern spiral galaxies:ESO598-G009,NGC1515 and NGC7456. Isophotal map, luminosity profile, ellipticity profile and position angle profile were obtained for these galaxies using SPIRAL package. The results show that one of the galaxies, ESO598-G009 has relatively large bulge component and changes in position angle due to spiral arms. The NGC7456 has very small bulges; and the isophotal map of the NGC1515 shows that it is a typical spiral galaxy with bar.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.89.1-89.1
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• 2017

In this poster, we present standard calibration processes and results for photometry of $H-{\alpha}$ filter using broadband filters. We took data from a night in stable weather condition. And we derived parameters for band pass calibration including color terms. The corrected photometry results from broadband filters like V and R filters showed high correlation enough to replace instrumental $H-{\alpha}$ magnitude. We plan to extend these standardizing processes to another narrowband filters and flux calibration of narrowband filters from photometry of PNe.

• Journal of The Korean Astronomical Society
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• v.31 no.1
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• pp.67-74
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• 1998

The VI CCD photometry is made for stars in the globular cluster M22 down to $V\approx19^m,\;I\approx18^m$. In the color-magnitude diagram (CMD), red giant branch (RGB), asymtotic giant branch (AGB) and blue horizontal branch (BHB) are well defined. The luminosity functions (LF) of RGB, AGB and BHB stars are derived, discussing deficient gaps and bumps in the CMD. The anomalously wide RGB seen in the BV photometric system is found to disappear in the VI photometric system.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.58.1-58.1
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• 2017

National Youth Space Center has recently founded the Deokheung Optical Astronomy Observatory (DOAO) 1m Telescope, which accepts community observing applications since 2016. Standardization and calibration of the new observing facility are essential for astronomical research. In this poster, we present standardization processes and preliminary results for photometry of the Johnson-Cousins BVRI filter system. We selected sample data from a night in stable weather condition. After bias, dark, and flat corrections and photometry using ccdred and daophot package of IRAF, we derived standardized band pass parameters including color terms. The corrected photometry results of the BVRI filter system show reduced deviations from the standard magnitudes in the literature. In addition, we calculated atmospheric extinction coefficients and limiting magnitudes of the telescope system. We plan to extend these standardizing processes to flux calibration of narrow band filters, e.g. $H{\alpha}$ filter.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.101-106
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• 2008

Zonal cavity method, which is a kind of the lumen method, is used the calculation of the average illuminance on the workplane in an interior. Important factors of the method are cavity ratio, coefficient of utilization, and light loss factor. A Coefficient of Utilization varies with a kind of luminaires and is affected by surface reflectance of space. For this, the data from Coefficient of Utilization computation were analyzed with the same lumens and different photometry. This paper analyzes the changes of Coefficients of Utilization on the photometry of luminaires and surface reflectance of space.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.194-201
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• 1997

We have carried out JK near-infrared photometry for the central region of the metal rich globular cluster M71, whose (K, J - K) color-magnitude diagram is presented here. Using two independent methods we derive the distance modulus to M71, 12.89 and 12.86 $pm0.12$ respectively. The former is derived using the HB luminosity $M_{Ko}$(HB) = -1.15 for globular clusters having metallicity between -1.0 to -0.3 (Kuchinski et al. 1995). The latter is derived through a comparison with IR photometry of stars in the similar metallicity cluster 47 Tuc. We also estimate the reddening to M71, E(J - K) = 0.13, based on E(B - V) = 0.04 of 47 Tuc.

• Journal of The Korean Astronomical Society
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• v.31 no.2
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• pp.141-160
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• 1998

We have conducted BV RI CCD surface photometry of three spiral galaxies ESO 598-G009, NGC 1515 and NGC 7456. In order to understand the morphological properties and luminosity distribution characteristics for each galaxy, we derived isophotal map, position angle profile, ellipticity profile, luminosity profile, color profile and color contour map. ESO 598-G009, which has a bright bulge component and a ring, shows a trace of gravitational interaction. NGC 1515 is a spiral galaxy with a bar and dust lane. NGC 7456 shows typical characteristics of a late type spiral galaxy.