• Publications of The Korean Astronomical Society
• /
• v.8 no.1
• /
• pp.185-197
• /
• 1993

We developed an Automatized Differential Photometry System (ADPS) to achieve high time resolution and high efficiency in the photometric observations of short period variable stars. This ADPS has been introduced to the CCD camera system attached to the 6lcm Reflector at Sobaeksan Astronomy Observatory. Several new algorithms were devised for the controlling the telescope. the star recognition in a CCD frame and the aperture photometry, etc..As the result, the differential photometric observation was fully automatized without any manual control, and much faster data acquisition could be achieved over the conventional photoelectric differential photometry.

• Publications of The Korean Astronomical Society
• /
• v.8 no.1
• /
• pp.67-82
• /
• 1993

We developed a real-time CCD photometric program for IBM PC compatibles. This program can perform several functions necessary for CCD photometry such as telescope control. filter rotation, CCD camera control and data acquisition, two-dimensional image processing, simple aperture photometry and automatic differential photometry. The image processing of a spiral galaxy M51 observed with the SNU 61cm reflector shows a well developed spiral structure. Simple aperture photometric results of 14 stars in open cluster NGC 6871 almost accorded with those from IRAF/APPHOT. And we could confirm the light variation of eclipsing binary EM Cep by simultaneous automatic differential photometry of 7stars in NGC 7160. Due to the excellence in the precision and efficiency of automatic differential photometry using CCD. this program is very useful for the study of small amplitude ${\delta}$ Sct type variables and of the photometric stability of B ${\sim}$ F type stars.

• Journal of The Korean Astronomical Society
• /
• v.28 no.2
• /
• pp.197-208
• /
• 1995

Real time CCD differential photometry was performed for BT Cnc in Praesepe cluster from February to March, 1994. New 885 differential V magnitudes were obtained for thirteen nights. From the frequency analysis, we have detected two distinct pulsational frequencies of $f_1$=9.7783c/d and $f_2$=7.0153c/d. The first frequency is nearly equal to the previous result(Breger 1980), but the second one is much different. Our reanalysis of the previous data obtained by Guerrero el al.(1979) indicates that the previous result of $f_s$=5.95c/d might be uncertain; it was not detected in the power spectrum. Also it turns out that our second frequency could not be fitted to the previous data and the reanalyzed frequency($f_2$=7.8813c/d) of the previous data was poor-fitted to our data. Therefore we suggest that the second frequency which might be newly excited in the nonradial mode, has been changed over the last eighteen years.

• Journal of The Korean Astronomical Society
• /
• v.25 no.2
• /
• pp.91-104
• /
• 1992

New photoelectric UBV Photometry of 112 stars in open cluster M35 field was obtained. The distance modulus and age of the cluster are $9.^m3$(725pc) and $8.5{\times}10^7yrs$, respectively. The internal differential reddening within the cluster is apparent.

• The Bulletin of The Korean Astronomical Society
• /
• v.17
• /
• pp.12.2-13
• /
• 1992

• The Bulletin of The Korean Astronomical Society
• /
• v.7
• /
• pp.10.2-10.2
• /
• 1982

• Bulletin of the Korean Space Science Society
• /
• 1996.05a
• /
• pp.11-11
• /
• 1996

No Abstract, See Full Text

• Journal of Astronomy and Space Sciences
• /
• v.18 no.1
• /
• pp.55-62
• /
• 2001

We present VRI CCD photometry of W UMa type binary TY UMa. The light curves show that the secondary minimum is deeper than the primary minimum and the maximum I ($0.^{p}25$)is $0.^{m}023$ brighter than the maximum II ($0.^{p}75$). The V light curve has been analyzed and the photometric solutions have been determined by the method of Wilson & Devinney differential correction. We adopted the spot model to explain the asymetric light curve.

• Journal of Astronomy and Space Sciences
• /
• v.16 no.2
• /
• pp.241-254
• /
• 1999

Differential time-series observations of BL Camelopardalis classified as a double mode SX Phoenicis type variable were secured with a charge coupled device. The observed photometric data was reduced using the IRAF Package and the differential magnitudes were obtained through aperture photometry. The periods of BL Cam were analyzed with the Generalized Least-Square Method by Vanicek (1971) and the Fourier Decomposition Method. It was found that the first and second period of BL Cam were 0.0391 day respectively which lead the period ratio of P1/P0=0.81. This period ratio is much different from 0.78 determined by other investigators and also much more larger than that of other double-mode SX Phe type variables. In addition, this period ratio is much different from the value expected from the relation between the metallicity and period ratio. From these results, it can be confirmed that BL Cam is the most extreme case among all double-mode SX Phe type variables.

• Journal of Astronomy and Space Sciences
• /
• v.33 no.2
• /
• pp.127-135
• /
• 2016

Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.