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 \pm 3 pc , and an estimated tangential velocity of v _ { { t } } = 50 \pm 10 km s ^ { -1 } .