  We describe and characterize a 25 GHz laser frequency comb based on a
cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform
array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by
use of a global positioning system referenced atomic clock. This comb was
deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where
it was used as a radial velocity calibration source for the fiber-fed
Pathfinder near-infrared spectrograph. Stellar targets were observed in three
echelle orders over four nights, and radial velocity precision of \sim10 m/s
(\sim6 MHz) was achieved from the comb-calibrated spectra.
