We present a BV I optical photometric study of the old open cluster Ruprecht 6 using the data obtained with the SMARTS 1.0 m telescope at the CTIO, Chile. Its color-magnitude diagrams show the clear existence of the main-sequence stars, whose turn-o point is located around V  18:45 mag and B - V  0:85 mag. Three red clump (RC) stars are identied at V = 16:00 mag, I = 14:41 mag and B - V = 1:35 mag. From the mean Ks-band magnitude of RC stars (Ks = 12:39  0:21 mag) in Ruprecht 6 from 2MASS photometry and the known absolute magnitudes of the RC stars (MKS = - :595  0:025 mag), we obtain the distance modulus to Ruprecht 6 of (m -M)0 = 13:84  0:21 mag (d = 5:86  0:60 kpc). From the (J - Ks) and (B - V ) colors of the RC stars, comparison of the (B - V ) and (V - I) colors of the bright stars in Ruprecht 6 with those of the intrinsic colors of dwarf and giant stars, and the PARSEC isochrone ttings, we derive the reddening values of E(B - V ) = 0:42 mag and E(V - I) = 0:60 mag. Using the PARSEC isochrone ttings onto the color-magnitude diagrams, we estimate the age and metallicity to be: log(t) = 9:50  0:10 (t = 3:16  0:82 Gyr) and [Fe/H] = -0:42  0:04 dex. We present the Galactocentric radial metallicity gradient analysis for old (age > 1 Gyr) open clusters of the Dias et al. catalog, which likely follow a single relation of [Fe/H] = (-0:034  0:007)RGC + (0:190  0:080) (rms = 0.201) for the whole radial range or a dual relation of [Fe/H] = (-0:077  0:017)RGC + (0:609  0:161) (rms = 0.152) and constant ([Fe/H]  -0:3 dex) value, inside and outside of RGC  12 kpc, respectively. The metallicity and Galactocentric radius (13:28  0:54 kpc) of Ruprecht 6 obtained in this study seem to be consistent with both of the relations.

We present analyses of 1250 variable sources identied in a 20 square degree eld toward NGC 2784 by the KMTNet Supernova Program. We categorize the variable sources into three groups based on their B-band variability. The rst group consists of 31 high variability sources with their B- band RMS variability greater than 0.3 magnitudes. The second group of medium variability contains 265 sources with RMS variability between 0.05 and 0.3 magnitudes. The remaining 951 sources belong to the third group of low variability with an RMS variability smaller than 0.05 magnitudes. Of the entire 1250 sources, 4 clearly show periods of variability greater than 100 days, while the rest have periods shorter than 51 days or no reliable periods. The majority of the sources show either rather irregular variability or short periods faster than 2 days. Most of the sources with reliable period determination between 2 and 51 days belong to the low-variability group, although a few belong to the medium-variability group. All the variable sources with periods longer than 35 days appear to be very red with B􀀀V > 1.5 and V 􀀀I > 2.1 magnitudes. We classify candidates of 51 Cepheids, 17 semi-regular variables, 3 Mira types, 2 RV(B) Tauri stars, 26 eclipsing binary systems and 1 active galactic nucleus. The majority of long-term variables in our sample belong to either Mira or semi-regular types, indicating that long-term variability may be more prominent in post-main sequence phases of late-type stars. The depth of the eclipsing dips of the 26 candidates for eclipsing binaries is equivalent to 0.61 as the average relative size of the two stars in the binary system. Our results illustrate the power of the KMTNet Supernova Program for future studies of variable objects.