We present the color-magnitude diagrams (CMD) of more than 24,000 stars in the field of an intermediate age open cluster M11, based on wide field CCD imaging. The morphology of the CMDs varies strikingly as the distance from the center of the cluster increases. From the surface number density analysis, we confirm the mass segregation effect in this cluster: the bright, massive stars are centrally more concetrated than the faint, low mass stars. The slope of the field-corrected surface density with respect to magnitude progressively increases as the radius increases, up to r = 5'. Most of the field stars in or near the cluster main sequence band and in the bright part of the red stars in the CMDs appear to be nearly at the same distance as M11, and they are considered to be the major component of disk stars in the Sagittarius-Carina arm.

We present a study of the metallicity of the old open cluster NGC 1245 , based on the Washington CCD photometry obtained using the 0.6 m telescope at the Sobaeksan Observatory, Korea. NGC 1245 has been known to be a unique cluster among the known open clusters in the sense that the previous metallicity estimates for this cluster are much larger (by 3σ) than the value expected from the radial metallicity gradient of the old open clusters in Our galaxy. We have estimated the metallicity of the cluster red giants using the four color-color diagrams, obtaining a value for the mean metallicity of [Fe/H] = -0.04±0.05 dex. The total error including the error of the metallicity calibration, 0.15 dex, is 0.16 dex. The metallicity estimate of NGC 1245 we have obtained in this study is smaller than previous estimates, and is consistent with the radial metallicity gradient of the old open clusters, showing that the mean metallicity of NGC 1245 is not abnormally high. The reddening, distance, and age of the cluster have also been derived using the isochrones based on the convective overshooting models: the reddening E(B-V) = 0.28±0.03; the distance d = 2.5±0.2 kpc (the corresponding galactocentric distance is RGC = 10.7 kpc, and the distance from the galactic plane is z = -0.4 kpc); and the age t = 1.1±0.1 Gyrs.

NGC 6716 is an intermediate-age open cluster in Sagittarius. In this paper, we present the new UBV CCD photometry of the stars in the cluster, which is deeper than previous ones. From the color-color diagram and the color-magnitude diagram, we derived a reddening EB- V = 0.17±0.03 and a distance modulus of the cluster, (V - Mv)o = 9.2±0.1. An age of the cluster is estimated as 8 × 107 yrs from the latest isochrone. Luminosity function and mass function of the cluster are derived. The gradient of the mass function of bright stars is a bit steep, Γ = -1.85±0.05, and there is no distinct bump and dip in the mass function.

We present test results of time-series CCD photometry to investigate the photometric precision of the BOAO (Bohyunsan Optical Astronomy Observatory) 1.8m telescope. A well-known field of the old open cluster M67, which includes two pulsating blue stragglers and two W UMa type binaries, was monitored for 3.5 hours on February 22, 1996. We have collected 148 V frames and 3 B frames. Photometric noises which consist mainly of photon noise and scintillation noise, were lowered down to about 1.9 mmag for stars of 10.m5 in M67 with exposure time of 20 seconds. From the C-M diagram for M67, a number of observational properties were derived; E(B-V) = 0.03, (V-Mv)o = 9.6, Age = 4 Gyr. We obtained light curves for four known variable stars and confirmed their variational characteristics. The pulsating blue stragglers show a low amplitude (about 0.01 mag) of light variation.

We present results of time-series CCD photometry for 178 stars in the young open cluster M29 (=NGC6913). Total 1036 V-band CCD frames were collected for five nights between August 12 and September 13, 1994. The photometric precision is about 7.6 mmag for 9th-10th mag stars in M29 with exposure times of 30 seconds. From the dispersion diagram and the light curves, one detached eclipsing binary (HD194378) and two suspected variables are newly discovered. A ɤ Cas type variable, V1322 Cyg, which has been known as a member of M29, did not show any light variations during the period of present observations, indicating that it passed the steady phase without the eruption during our observing runs.

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 f1=9.7783c/d and f2=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 f3=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(f2=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.

New photoelectric UBV Photometry of 112 stars in open cluster M35 field was obtained. The distance modulus and age of the cluster are 9. m 3 (725pc) and 8.5 × 10 7 y r s , respectively. The internal differential reddening within the cluster is apparent.