In the region of the open cluster M48 (NGC 2548), time-series BV CCD images were taken for 22 nights from February 28 in 2008 to March 17 in 2011. From this observation, we found 10 new variable stars. They include five eclipsing binaries, an RR Lyrae, two δ Scuti, and two semi-periodic and/or slow irregular type variable stars. We fail to find the member stars of the open cluster among the 10 variable stars.

UBV I CCD photometry of NGC 2353 is performed as a part of the "Sejong Open cluster Survey" (SOS). Using photometric membership criteria we select probable members of the cluster. We derive the reddening and distance to the cluster, i.e., E(B - V ) = 0.10 ± 0.02 mag and 1.17 ± 0.04 kpc, respectively. We find that the projected distribution of the probable members on the sky is elliptical in shape rather than circular. The age of the cluster is estimated to be log(age)=8.1 ± 0.1 in years, older than what was found in previous studies. The minimum value of binary fraction is estimated to be about 48 ± 5 percent from a Gaussian function fit to the distribution of the distance moduli of the photometric members. Finally, we also obtain the luminosity function and the initial mass function (IMF) of the probable cluster members. The slope of the IMF is Γ = -1.3 ± 0.2.

We study near-infrared properties of the old open cluster King 11, based on the 2MASS photometric data. We determine the location of the red giant clump(RGC) in the (K, J - K) colo-magnitude diagram and derive the distance modulus of King 11 to be (m-M)0 = $12.50 ± 0.10 using the mean K magnitude of RGC. From the red giant branch slope - [Fe/H] relation we obtain the metallicity of this cluster, [Fe/H]=-0.17±0.07. The age and interstellar reddening of this cluster are estimated to be log t = 9.48±0.05, E(B-V)=0.90±0.03, by applying Padova isochrone fits to the data.

In the region of the intermediate open cluster M35 (NGC 2168), the time-series of V CCD images was taken for 12 nights from December 18, 2007 to September 25, 2010. From this observation, we detected 22 variable stars including 15 new ones. They are 6 δ Scuti, a Cepheid, an RR Lyrae, 9 eclipsing binaries and 5 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the δ2 Scuti stars, the multi-frequency analysis was performed using the Discrete Fourier Transform and the linear least-square fitting.

UBVI CCD photometry is obtained for the Ruprecht 93 (Ru 93)region. We are unable to confirm the existence of an intermediate-age open cluster in Ru 93 from the spatial distribution of blue stars. On the other hand, we find two young star groups in the observed field: the nearer one (Ru 93 group) comprises the field young stars in the Sgr-Car arm at d ≈ 2.1 kpc, while the farther one (WR 37 group) is the young stars around WR 37 at d ≈ 4.8 kpc. We derive an abnormal extinction law (RV = 3.5) in the Ruprecht 93 region.

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: 6δ Scuti stars, 2γ Doradus stars, 18 eclipsing binaries and 18 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the δ Scuti and γ 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.

We present JHK near-infrared photometric study for the old open cluster (OC) Trumpler 5 (Tr 5), based on the 2MASS data. From the color-magnitude diagrams of Tr 5, we have located the position of the red giant clump (RGC) stars, and used the mean magnitude of the RGC stars in K-band to estimate the distance to Tr 5, d = 3:1±0:1 kpc ((m-M)0 = 12:46±0:04). From fitting the theoretical isochrones of Padova group, we have estimated the reddening, metallicity, and age : E(B-V ) = 0:64±0:05, [Fe/H] = -0:4 ± 0:1 dex, and t = 2:8 ± 0:2 Gyr (log t = 9:45 ± 0:04), respectively. These parameters generally agree well with those obtained from the previous studies on Tr 5 and confirms that this cluster is an old OC with metallicity being metal-poorer than solar abundance, located in the anti-Galactic center region.

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, I obtained time-series BV CCD images in the region of the young open cluster M29 (NGC 6913) for 15 nights from May 30, 2008 to September 17, 2009. I observed 48 variable stars including 45 new ones. They consisted of 5 δ Scuti, a Cepheid, 16 eclipsing binaries and 24 semi-long periodic and/or slow irregular type variable stars including β Cephei and LPB type stars. For the rest two ones, the type of variability was not defined. I also checked the variability of the 26 known variable stars listed in the GCVS. Only three ones among 26 known variable stars confirmed variability.

From the short-period variability survey (SPVS) in Bohyunsan Optical Astronomy Observatory, we obtained time-series BV CCD images in the region of an open cluster M38 (NGC 1912) for 23 nights from February 1, 2007 to December 7, 2008. We found 18 δ Scuti stars and 2 γ Doradus stars. Among them, only 3 δ Scuti stars were known ones. From the color-magnitude diagram (CMD) of M38, most of them have been located in the instability strip. The two γ Doradus stars have been located within γ Doradus strip of M38. But, only four δ Scuti stars were located within radius 10' from the center of M38. To confirm of their membership for M38, we need more study, such as, proper motion by spectroscopic observation.

We present UBV I photometry of the old open cluster NGC 1193. Color-magnitude diagrams (CMDs) of this cluster show a well defined main sequence and a sparse red giant branch. For the inner region of r < 50′′, three blue straggler candidates are newly found in addition to the objects Kaluzny (1988) already found. The color-color diagrams show that the reddening value toward NGC 1193 is E(B − V ) = 0.19 ± 0.04. From the ultraviolet excess measurement, we derived the metallicity to be [Fe/H]= −0.45 ± 0.12. A distance modulus of (m −M)0 = 13.3 ± 0.15 is obtained from zero age main sequence fitting with the empirically calibrated Hyades isochrone of Pinsonneault et al. (2004). CMD comparison with the Padova isochrones by Bertelli et al. (1994) gives an age of log t = 9.7±0.1.

From the short-period variability survey (SPVS), we obtained time-series BV CCD images in the region of an open cluster M50 (NGC 2323) for 10 nights from 2008 February 9 to 27. The observation was performed using a small refracting telescope ( ϕ=155mm, f=1050mm) in Bohyunsan Optical Astronomy Observatory (BOAO). M50 is included in the observing field of ASAS (The All Sky Automated Survey). In the region of M50, we found 8 new variable stars including two δ Scuti stars with short-periods and very small amplitudes. There are known nine variable stars by the catalogues of ASAS and GCVS in the region. We confirmed the variability of the known variable stars for six and non-variability for three.

소형망원경을 이용하여 산개성단 내 단주기 미세 변광성을 체계적으로 탐사하기 위한 보현산 천문대 측광 모니터링 프로그램 Short Period Variability Survey(SPVS)의 일환으로, 젊은 산개성단 NGC 129의 90'×60' 영역에 대한 V필터 시계열 측광 관측을 수행하였다. 성단의 관측은 보현산 천문대 155mm 소형 굴절 망원경과 3K×2K CCD 카메라를 이용하여 2004년 10월 12일부터 2005년 11월 3일까지 총 11일간 수행되었으며, 그 결과 전체 2400장의 V 필터시계열 CCD 영상자료 및 성단의 색-등급도를 얻었다. 시계열 자료의 기기등급을 표준등급으로 변환하기 위하여 앙상블정규화 기법(ensemble normalization technique)을 사용하였다. 측광 후 총 9537개별의 시간에 따른 광도변화를 조사한결과 총 66개의 새로운 변광성을 발견 하였다. 새롭게 찾아낸 변광성들은 DFT(Discrete Fourier Transform) 분석과 위상 맞추기 방법(phase-matching technique)을 이용하여 변광 주기를 결정하였다. 결정된 변광성의 주기 및 진폭 변화, 색-등급도 상에서의 변광성의 위치 등을 고려하여 변광 유형을 조사한 결과 9개의 SPB형 변광성과 9개의 δ Scuti형 변광성, 29개의 식변광성, 17개의 장주기 변광성과 기타 2개의 변광성으로 분류할 수 있었다. 본 연구를 통해, 산개성단에서의 변광성 탐사 연구에 소형망원경이 유용하게 활용될 수 있음을 확인하였다.

UBVIJHK photometry of the open cluster NGC 2194 are presented. Color-Magnitude diagrams of this cluster show well-defined main sequence and red giant clump. The main sequence also contains clear evidence of binary populations. Based on color-color diagrams, absolute magnitude of red giant clump, ZAMS fitting, and comparisons of observed color-magnitude diagrams with theoretical models, we derive following parameters for the cluster; reddening E(B-V)=0.44±0.04, age of log t ~8.8, and finally distance of (m-M)0=12.20±0.18.