We present the results of an archival search for Trans-neptunian objects ( TNOs ) in an ecliptic field observed with Subaru in 2002 .
The depth of the search allowed us to find 20 new TNOs with magnitudes between R = 24 and 27 .
We fit a double power law model to the data ; the most likely values for the bright and faint power law exponents are \alpha _ { 1 } = 0.73 _ { -0.09 } ^ { +0.08 } and \alpha _ { 2 } = 0.20 _ { -0.14 } ^ { +0.12 } ; the differential number density at R = 23 is \sigma _ { 23 } = 1.46 _ { -0.12 } ^ { +0.14 } and the break magnitude is R _ { eq } = 25.0 _ { -0.6 } ^ { +0.8 } .
This is the most precise measurement of the break in the TNO luminosity function to date .
The break in the size distribution corresponds to a diameter of D = 90 \pm 30 km assuming a 4 % albedo .