• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.49.4-49.4
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• 2021

We Present a B and V band time-series CCD photometry of the Delta scuti stars, BV Cnc, BN Cnc, BU Cnc, BS Cnc, in the open cluster M44. The observation was carried out for 36 nights between February, 2020 and February 2021 with a 0.6m telescope equipped 2K CCD camera at Gyeonggi Science High School for the Gifted(GSHS). To detect pulsational frequencies, we wuse Discret Fourier Transformation(DFT) method. We have detected resonable pulsational frequencis compare to previous study.

• Journal of Photoscience
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• v.9 no.2
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• pp.290-292
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• 2002

The intermediate M420 formed in a solution of firefly luciferin in deoxygenated dimethyl-sulfoxide added potassium f-butoxide was observed to emit yellow-green and red light by filter-photometry. By H-NMR, M420 was found to be deprotonated at the site where luciferin reacts with oxygen.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.144.1-144.1
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• 2011

We explore the metallicity distribution of the Galactic halo based on the SDSS ugriz photometry. We use empirically calibrated sets of stellar isochrones to determine distances and metallicities of individual main-sequence stars in the halo. At heliocentric distances greater than 5 kpc, we find that the in situ photometric metallicity distribution reveals chemically divided dual halo components, which supports arguments from earlier studies based on the medium resolution spectroscopy. Our finding provides an unbiased estimate of relative fractions of each of these stellar components in the Galactic halo.

• The Bulletin of The Korean Astronomical Society
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• v.6
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• pp.3-6
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• 1981

A scheme for installing the digital printing devices as an additional output system of photoelectric photometry is discussed. The digital printing devices consist of counter/integrator and printer interfaces for the digital printer HP 5055A. The integration gate time could be adjusted from 1 second to 99 seconds.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.56.2-56.2
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• 2016

We present a multi-aperture photometry pipeline for DEEP-South (Deep Ecliptic Patrol of the Southern Sky) time-series data, written in C. The pipeline is designed to do robust high-precision photometry and calibration of non-crowded fields with a varying point-spread function, allowing for the wholesale search and characterization of both temporal and spatial variabilities. Our time-series photometry method consists of three parts: (i) extracting all point sources with several pixel/blind parameters, (ii) determining the optimized aperture for each source where we consider whether the measured flux within the aperture is contaminated by unwanted artifacts, and (iii) correcting position-dependent variations in the PSF shape across the mosaic CCD. In order to provide faster access to the resultant catalogs, we also utilize an efficient indexing technique using compressed bitmap indices (FastBit). Lastly, we focus on the development and application of catalog-based searches that aid the identification of high-probable single events from the indexed database. This catalog-based approach is still useful to identify new point-sources or moving objects in non-crowded fields. The performance of the pipeline is being tested on various sets of time-series data available in several archives: DEEP-South asteroid survey and HAT-South/MMT exoplanet survey data sets.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.165-174
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• 2006

The autotstigmatic null lens system is designed and constructed for the fabrication of a parabolic mirror with the diameter of 450 mm(f/2.7). And the measurement reliability is also analyzed theoretically by means of the tolerancing technique using lens design software(CODE V). From this analysis, we can precisely fabricate a parabolic mirror with the large diameter of 450 mm(f/2.7). Meanwhile, in order to confirm the fabrication results by the autostigmatic method, the mirror surface is tested again by an autocollimating method that uses only a plane mirror without any null lens.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.56-62
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• 2005

Because of the wide plane and the curved field of CRT rear projection high definition television, its MTF(modulation transfer function) can't be easily measured by the usual forward testing method. Then we propose a backward testing method for the MTF so that the object plane and the image analyzer of forward testing are located at positions opposite each other. We prefer to use the backward testing method because the forward testing method has poor accuracy caused by very small numerical aperture, low spatial resolutions, and long depth of focus. We found that the backward testing method was very easy to align and had high repeatability. We confirmed the confidence of results obtained by the backward testing method in comparison with designed results.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.50-55
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• 2005

A method for measuring the wavefront error and the modulation transfer function(MTF) of large aperture optics using an unequal path interferometer is presented. A bidirectional shearing interferometer is used for collimation testing of the measurement system. A large aperture Fizeau interferometer with long optical path difference measures the wavefront error of the optics under test by using a $\Phi$ 400 mm off-axis parabolic mirror. The MTF is also measured at the wavelength of the interferometer by changing the laser light into partially incoherent light. Test results of a $\Phi$ 300 mm Cassegrain type satellite telescope made in Korea are presented.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.63-70
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• 2005

We propose a method for evaluating the image quality of color liquid crystal display(LCD) monitors by using the polychromatic modulation transfer function(PMTF), which is calculated from the modulation transfer function(MTF) weighted by the overall color response of the system including the test LCD monitor. We confirm that experimental results using the PMTF agree well with simulated results of the PMTF of a color LCD monitor by using three bar targets with different amplitudes and three elementary colors such as red(R), green(G), and blue(B). As a results, we should choose the PMTF instead of the white color MTF or monochromatic MTF in order to evaluate correctly the image quality of color LCD monitors.

• Journal of Astronomy and Space Sciences
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• v.38 no.1
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• pp.45-53
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• 2021

GLONASS, a satellite navigation system developed in Russia since 1976, is defunct and orbits in an unstable attitude. The satellites in these problems are not managed and there is no precise information, which can increase the risk of collisions with other space objects. In this study, detailed attitude dynamic have to be analyzed through photometry data, which requires spin period and spin axis. The light curve data is obtained by observing through the photometer at the Graz station and the power spectrum is calculated to obtain the cycle of the satellite. The geometric relationship between observer and sun is analyzed for GLONASS-50 satellite. The box-wing model is applied to obtain the phase reflection of the satellite and obtain the Irradiation of the satellite through this information. In Light Curve and Irradiation, the spin axis is calculated for each peak points with the distance square minimum technique. The spin axis of the GLONASS-50 satellite is RA = 116°, Dec = 92°.