  We present the discovery of a T dwarf, 2M2151-4853, via differential imaging
through methane filters. The filters are designed to highlight the strong
absorption in the H band, due to methane found in the atmospheres of T dwarfs,
and provide a very efficient means of searching for them. Subsequent J and H
band spectroscopy confirms 2M2151-4853 as a T dwarf of type T4.5. It has an
estimated spectrophotometric distance of 18 +/- 3 pc, and an estimated
tangential velocity of v=50 +/- 10 km/s.
