The Globular Cluster NGC 6402 (M14). I. A New BV Color-Magnitude Diagram
  We present BV photometry of the Galactic globular cluster NGC 6402 (M14),
based on 65 V frames and 67 B frames, reaching two magnitudes below the
turn-off level. This represents, to the best of our knowledge, the deepest
color-magnitude diagram (CMD) of NGC 6402 available in the literature.
Statistical decontamination of field stars as well as differential reddening
corrections are performed in order to derive a precise ridgeline and derive
physical parameters of the cluster therefrom.
  We discuss previous attempts to derive a reddening value for the cluster, and
argue in favor of a value E(B-V) = 0.57 +/- 0.02, which is significantly higher
than indicated by either the Burstein & Heiles or Schlegel et al. (corrected
according to Bonifacio et al.) interstellar dust maps. Differential reddening
across the face of the cluster, which we find to be present at the level of
Delta E(B-V) ~ 0.17 mag, is taken into account in our analysis. We measure
several metallicity indicators based on the position of the red giant branch
(RGB) in the cluster CMD. These give a metallicity of [Fe/H] = -1.38 +/- 0.07
in the Zinn & West scale and [Fe/H] = -1.28 +/- 0.08 in the new Carretta et al.
(UVES) scale. We also provide measurements of other important photometric
parameters for this cluster, including the position of the RGB luminosity
function "bump" and the horizontal branch (HB) morphology. We compare the NGC
6402 ridgeline with the one for NGC 5904 (M5) derived by Sandquist et al., and
find evidence that NGC 6402 and M5 have approximately the same age, to within
the uncertainties -- although the possibility that M14 may be slighlty older
cannot be ruled out.
