• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.48 no.6
• /
• pp.27-34
• /
• 2011

In this paper, we propose an active 3D shape acquisition method based on photometric stereo using camera and flash on a smartphone. Two smartphones are used as the master and slave, in which the slave projects illumination from different locations while the master captures the images and processes photometric stereo algorithm to reconstruct 3D shape. In order to reduce the error, the smartphone's camera is calibrated to overcome the effect of the lens distortion and nonlinear camera sensor response. We apply 5-point algorithm to estimate the pose between smartphone cameras and then estimate lighting direction vector to run the photometric stereo algorithm. Experimental result shows that the proposed system enables us to use smartphone as a 3D camera with low cost and high quality.

• Journal of The Korean Astronomical Society
• /
• v.10 no.1
• /
• pp.31-38
• /
• 1977

To reduce the instrumental and calibration errors in the photoelectric photometry as much as possible it is necessary to select the optimum photocell voltage and energy attenaution and to observe as many standard stars as possible over the wide range of color, spectral type and air mass.

• Journal of The Korean Astronomical Society
• /
• v.20 no.2
• /
• pp.63-94
• /
• 1987

Using many homogeneous data of DDO and UBV colors for all luminosity classes and physical quantities known from spectroscopic observations, new calibration schemes with DDO photometric parameters are presented for metal abundance, effective temperature and surface gravity of stars. And an intrinsic color relation is derived for the reddening estimate.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.3
• /
• pp.179-185
• /
• 2013

Photometric observation is one of the most effective techniques for determining the physical characteristics of unknown space objects and space debris. In this research, we examine the change in brightness of the Communication, Ocean, Meteorological Satellite-1 (COMS-1) Geostationary Orbit Satellite (GEO), and compare it to our estimate model. First, we calculate the maximum brightness time using our calculation method and then derive the light curve shape using our rendering model. The maximum brightness is then calculated using the induced equation from Pogson's formula. For a comparison with our estimation, we carried out photometric observation using an optical telescope. The variation in brightness and the shape of the light curve are similar to the calculations achieved using our model, but the maximum brightness shows a slightly different value from our calculation result depending on the input parameters. This paper examines the photometric phenomenon of the variation in brightness of a GEO satellite, and the implementation of our approach to understanding the characteristics of space objects.

• Journal of Astronomy and Space Sciences
• /
• v.20 no.4
• /
• pp.249-260
• /
• 2003

CCD photometric observations of a W UMa type contact binary AH Cnc were performed for ten nights from December 1998 to May 1999 using a PM512 CCD camera and BVI filters attached to the 61㎝ reflector at Sobaeksan Optical Astronomy Observatory. New BVI light curves were analyzed with contact Mode 3 of the Wilson-Devinney binary model. We obtained photometric solutions and Roche geometry of this binary system. Through the analysis of the (O-C) diagram with all times of minimum light published so far and including hour's secular variations of orbital period and the mass transfer rate were calculated.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.4
• /
• pp.213-221
• /
• 2013

We present the first BVRI CCD photometric observations of V345 Cas made on 22 nights during the observing seasons in 2007-2008. Our light curves, resembling those of EB-type binary stars, are analyzed with the 2003 version of the Wilson-Devinney binary code. The photometric study shows that V345 Cas is a typical semi-detached binary system with the primary star being about ${\Delta}T$ = 2400 K hotter, two times more massive, but only 17% larger than the secondary star being filled with it's Roche-lobe. The orbit has a relatively large inclination of about $88^{\circ}$. A cool spot on the secondary component is modeled to explain a small light curve asymmetry. Absolute dimensions and related radiometric parameters of the eclipsing pair are calculated and their evolutionary states are discussed with the HR diagrams of mass-radius and temperature-luminosity. A period analysis of all available times of minima, including our measurements, indicates that the orbital period may vary in a cyclical way, unfortunately the secondary period for the variation can not be uniquely determined because of lack of present timing data.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.5
• /
• pp.1-14
• /
• 2014

This study has found out appropriate scopes of correlated color temperature and illuminance value with regard to general diffused lighting and work in the kitchen. It also has presented appropriate photometric quantity control speed for behavioral change with the following results. 1)For general diffused lighting, the appropriate photometric quantity has turned out to be 4,000 to 4,500K in color temperature and illuminance value of 300 to 400lx. And 300lx at 4,500K has proven to be the most comfortable, behavior-appropriate, and preferred pair. 2)As far as appropriate photometric quantity for work is concerned, color temperature of 4,000 to 5,000K and illuminance value of 600 to 800lx are appropriate, while 700lx at 4,500 to 5,000K are the most comfortable, behavior-appropriate, and preferred set. 3)As for appropriate photometric quantity control speed in behavioral change, 3 to 5 seconds has proven the most comfortable, appropriate, and preferred for behavioral change from entry to general areas and 1 to 3 seconds for change from general to work.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.265-266
• /
• 2015

A search for luminous white dwarfs (WDs) in several nearby Galactic globular clusters (GCs) was carried out using the deep and homogeneous photometric catalog of Galactic GCs taken with the ACS/WFC aboard the Hubble Space Telescope (HST) by Sarajedini et al. and Anderson et al- It resulted in the identification of luminous WD candidates in the GCs M13 (NGC 6205) and M22 (NGC 6656). The purpose of the present study is to identify luminous WDs in the deep and homogeneous V versus V - I color-magnitude diagrams (CMDs) of several nearby Galactic GCs taken with the ACS/WFC aboard the HST. Using photometric data for the GCs M13 and M22 that are now in the public domain, the V versus V - I CMDs of the GCs M13 and M22 were constructed. Many spurious detections in the CMDs were removed using the photometric quality parameters qfit(V) and qfit(I), and a radial restriction was applied to the CMDs to remove the central stars with higher photometric errors due to central crowding. From each resultant V versus V - I CMD of the GCs M13 and M22, a dozen or so luminous WD candidates were identified. They were confirmed as stellar objects in the accompanying ACS/WFC images and their positions in the CMDs were in the bright part of the DA WD cooling curve. Therefore, the luminous WD candidates in the GCs M13 and M22 seem to be true luminous WDs, and spectroscopic observations are needed to confirm their true identity.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.41.2-41.2
• /
• 2015

We have performed deep wide-field CCD photometry of the young open cluster IC 1805 in the famous star forming region W4, and obtained photometric data for more than 91,000 stars in the field of IC 1805 based on observations with the 3.6m CFHT and the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The photometric data cover an area $43^{\prime}{\times}45^{\prime}$ which is far larger and far deeper than any other optical observations made for the cluster. In order to select the young stellar objects with mid-IR excess emission, we have performed mid-IR photometry of the cluster using the archival images obtained with the Spitzer Space Telescope IRAC and MIPS instruments. From a preliminary analysis of the data, we determined the reddening law ($R_V=3.02{\pm}0.05$), distance modulus ($V_0-M_V=11.9{\pm}0.2$), and the spatial distribution of members.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.50.4-51
• /
• 2015

Current and planned deep multicolor wide-area cosmological surveys will map in detail the spatial distribution of galaxies and quasars over unprecedented volumes, and provide a number of objects with photometric redshifts more than an order of magnitude bigger than that of spectroscopic redshifts. Photometric information is statistically more significant for studying cosmological evolution, dark energy, and the expansion history of the universe at a fraction of the cost of a full spectroscopic survey, but intrinsically carries a bias due to noise in the distance estimates. We provide convolution- and deconvolution-based algorithms capable of removing this bias -- thus able to exploit the full cosmological information -- in order to reconstruct intrinsic distributions and correlations between distance-dependent quantities. We then show some direct applications of our techniques to the VIMOS Public Extragalactic Redshift Survey (VIPERS) and the Sloan Digital Sky Survey (SDSS) datasets. Our methods impact a broader range of studies, when at least one distance-dependent quantity is involved; hence, they will be useful for upcoming large-volume surveys, some of which will only have photometric information.