  We have developed a near-infrared camera called ANIR (Atacama Near-InfraRed
camera) for the University of Tokyo Atacama Observatory 1.0m telescope
(miniTAO) installed at the summit of Cerro Chajnantor (5640 m above sea level)
in northern Chile. The camera provides a field of view of 5'.1 $\times$ 5'.1
with a spatial resolution of 0".298 /pixel in the wavelength range of 0.95 to
2.4 $\mu$m. Taking advantage of the dry site, the camera is capable of hydrogen
Paschen-$\alpha$ (Pa$\alpha$, $\lambda=$1.8751 $\mu$m in air) narrow-band
imaging observations, at which wavelength ground-based observations have been
quite difficult due to deep atmospheric absorption mainly from water vapor. We
have been successfully obtaining Pa$\alpha$ images of Galactic objects and
nearby galaxies since the first-light observation in 2009 with ANIR. The
throughputs at the narrow-band filters ($N1875$, $N191$) including the
atmospheric absorption show larger dispersion (~10%) than those at broad-band
filters (a few %), indicating that they are affected by temporal fluctuations
in Precipitable Water Vapor (PWV) above the site. We evaluate the PWV content
via the atmospheric transmittance at the narrow-band filters, and derive that
the median and the dispersion of the distribution of the PWV are 0.40+/-0.30 mm
for $N1875$ and 0.37+/-0.21 mm for $N191$, which are remarkably smaller
(49+/-38% for $N1875$ and 59+/-26% for $N191$) than radiometry measurements at
the base of Cerro Chajnantor (5100 m alt.). The decrease in PWV can be
explained by the altitude of the site when we assume that the vertical
distribution of the water vapor is approximated at an exponential profile with
scale heights within 0.3-1.9 km (previously observed values at night). We thus
conclude that miniTAO/ANIR at the summit of Cerro Chajnantor indeed provides us
an excellent capability for a "ground-based" Pa$\alpha$ observation.
