We present a color-magnitude (CM) diagram of M35, an open cluster. A DSLR camera was used for measuring the color index with the RGB channels. It is cost-effective and has relatively easy controls compared to astronomical CCDs for educational environments. The 8-inch refracting telescope was used at the Korea Science Academy of KAIST in Busan. The B-G color index was obtained from observations and the magnitudes from publications in order to draw CM diagram. The linear correlation of B-G to B-V is found. The RGB channel of the DSLR camera can be easily represented on the CM diagram for astronomical education with aid of easy controls.

We present a new tool for studying the spectral energy distributions (SEDs) and color-magnitude diagrams (CMDs) of galaxies and star clusters, BINARY STAR TO FIT (BS2fit). A key feature of this tool is that it takes the eects of binaries, stellar rotation and star formation history into account. It can be used to determine many parameters, including distance, extinction, binary fraction, rotational star fraction, and star formation history. Because more factors are included than in previous tools, BS2fit can potentially give new insight into the properties of galaxies and clusters. One can contact the authors for cooperation and helps via.

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.

From B ¨ o h m -Vitense's atmospheric model calculations, the relations, [ T e , (B-V)] and [B.C, (B-V)] with respect to heavy element abundance were obtained. Using these relations and evolutionary model calculations of Rood, and Sweigart and Gross, analytic expressions for some physical parameters relating to the C-M diagrams of globular clusters were derived, and they were applied to 21 globular clusters with observed transition periods of RR Lyrae variables. More than 20 different parameters were examined for each globular cluster. The derived ranges of some basic parameters are as follows; Y = 0.21 ∼ 0.33 , Z = 1.5 × 10 − 4 ∼ 4.5 × 10 − 3 , a g e , t = 9.5 ∼ 19 × 10 9 years, mass for red giants, m R G = 0.74 m ⊙ ∼ 0.91 m ⊙ , mass for RR Lyrae stars, m R R = 0.59 m ⊙ ∼ 0.75 m ⊙ , the visual magnitude difference between the turnoff point and the horizontal branch (HB), ${\Delta}V_{to}=3.1{\sim}3.4(<{\Delta}V_{to}>=3.32)$, the color of the blue edge of RR Lyrae gap, $(B-V)_{BE}=0.17{\sim}0.21=(<(B-V)_{BE}>=0.18),\;[\frac{m}{L}]_{RR}=-1.7{\sim}-1.9$, mass difference of m R R relative to m R G , ( m R G − m R R ) / m R G = 0.0 ∼ 0.39 . It was found that the ranges of derived parameters agree reasonably well with the observed ones and those estimated by others. Some important results obtained herein can be summarized as follows; (i) There are considerable variations in the initial helium abundance and in age of globular clusters. (ii) The radial gradient of heavy element abundance does exist for globular clusters as shown by Janes for field stars and open clusters. (iii) The helium abundance seems to have been increased with age by massive star evolution after a considerable amount (Y>0.2) of helium had been attained by the Big-Bang nucleosynthesis, but there is not seen a radial gradient of helium abundance. (iv) A considerable amount of heavy elements ( Z ∼ 10 − 3 ) might have been formed in the inner halo ( r G C <10 kpc) from the earliest galactic co1lapse, and then the heavy element abundance has been slowly enriched towards the galactic center and disk, establishing the radial gradient of heavy element abundance. (v) The final galactic disk formation might have taken much longer by about a half of the galactic age than the halo formation, supporting a slow, inhomogeneous co1lapse model of Larson. (vi) Of the three principal parameters controlling the morphology of C-M diagrams, it was found that the first parameter is heavy clement abundance, the second age and the third helium abundance. (vii) The globular clusters can be divided into three different groups, AI, BI and CII according to Z, Y an d age as well as Dickens' HB types. BI group clusters of HB types 4 and 5 like M 3 and NGC 7006 are the oldest and have the lowest helium abundance of the three groups. And also they appear in the inner halo. On the other hand, the youngest AI clusters have the highest Z and Y, and appear in the innermost halo region and in the disk. (viii) From the result of the clean separations of the clusters into three groups, a three dimensional classification with three parameters, Z, Y and age is prsented. (ix) The anomalous C-M diagrams can be expalined in terms of the three principal parameters. That is, the anomaly of NGC 362 and NGC 7006 is accounted for by the smaller age of the order of 1 ∼ 2 × 10 9 years rather than by the helium abundance difference, compared with M 3. (x) The difference in two Oosterhoff types I and II can be explained in terms of the mean mass difference of RR Lyrae variables rather than in terms of the helium abundance difference as suggested by Stobie. The mean mass of the variables in Oosterhoff type I clusters is smaller by 0.074 m ⊙ which is exactly consistent with Rood's estimate. Since it was found that the mean mass of RR Lyrae stars increases with decreasing Z, the two Oosterhoff types can be explained substantially by the metal abundance difference; the type II has Z< 3.4 × 10 − 4 , and the type I has higher Z than the type II.