We report infrared photometry of the extrasolar planet HD 209458b during the time of secondary eclipse ( planet passing behind the star ) .
Observations were acquired during two secondary eclipses at the NASA Infrared Telescope Facility ( IRTF ) in September 2003 .
We used a circular variable filter ( 1.5 % bandpass ) centered at 3.8 \mu m to isolate the predicted flux peak of the planet at this wavelength .
Residual telluric absorption and instrument variations were removed by offsetting the telescope to nearby bright comparison stars at a high temporal cadence .
Our results give a secondary eclipse depth of 0.0013 \pm 0.0011 , not yet sufficient precision to detect the eclipse , whose expected depth is \sim 0.002 - 0.003 .
We here elucidate the current observational limitations to this technique , and discuss the approach needed to achieve detections of hot Jupiter secondary eclipses at 3.8 \mu m from the ground .