We report recent ground-based photometry of the transiting super-Earth exoplanet GJ 1214b at several wavelengths , including the infrared near 1.25 \mu m ( J-band ) .
We observed a J-band transit with the FLAMINGOS infrared imager and the 2.1-meter telescope on Kitt Peak , and we observed several optical transits using a 0.5-meter telescope on Kitt Peak and the 0.36-meter Universidad de Monterrey Observatory telescope .
Our high-precision J-band observations exploit the brightness of the M-dwarf host star at this infrared wavelength as compared to the optical , as well as being significantly less affected by stellar activity and limb darkening .
We fit the J-band transit to obtain an independent determination of the planetary and stellar radii .
Our radius for the planet ( 2.61 ^ { +0.30 } _ { -0.11 } R _ { \oplus } ) is in excellent agreement with the discovery value reported by Charbonneau et al .
based on optical data .
We demonstrate that the planetary radius is insensitive to degeneracies in the fitting process .
We use all of our observations to improve the transit ephemeris , finding P = 1.5804043 \pm 0.0000005 days , and T _ { 0 } = 2454964.94390 \pm 0.00006 BJD .