CCD photometry of the Galactic globular cluster NGC 6144

We present CCD photometry in the BVI-filter passbands for the Galactic globular cluster NGC 6144. This cluster is located in the direction of the rho Ophiuchi dust cloud, approximately 30' northwest of the bright star alpha Scorpii (Antares). Our color-magnitude diagrams (CMDs) of NGC 6144 extend from above the tip of the first-ascent red giant branch (RGB) to similar to 3 mag below the horizontal branch (HB). The morphology of the HE is predominantly blueward of the RR Lyrae instability strip, while the RGB is relatively steep, signifying a low-to-intermediate metal abundance. Our CMD also reveals the presence of three candidate post-asymptotic giant branch stars. We find V-HB = 16.30 +/- 0.07; coupling the measured RGB color at the level of the HE with a polynomial describing the shape of the RGB, we have utilized the simultaneous reddening and metallicity method of Sarajedini to estimate a metallicity of [Fe/H] = -1.81 +/- 0.12 (on the Zinn & West scale) and a mean reddening of E(B - V) = 0.41 +/- 0.02. In addition to this mean level, our observations reveal that the reddening has a spatially variable component generally increasing from north to south consistent with the expected density variations in the rho Ophiuchi dust cloud.