We have used the coronographic instrument CoCo with the IRTF ’ s facility camera NSFCAM to obtain improved photometry at JHKL ^ { \prime } of the giant planet/brown dwarf Gliese 229B .
We have recalibrated the published spectra for this object , and re–calculated its luminosity .
Our L ^ { \prime } value , and our flux calibration of the spectra at JHK , are significantly different from those previously published .
Our results show good agreement at all bands except H with evolutionary models by Burrows et al .
which include grain condensation .
The model comparison implies that Gliese 229B is likely to be a 0.5 Gyr–old 25 M _ { J } object with T _ { eff } \sim 900 K .