The TIRGO NIR photometer uses a single InSb detector with cooled low-noise amplification electronics. Detector, filters, and diaphragms are cryogenically cooled to solid nitrogen temperature. The TIRGO NIR filter system closely approximates that of CalTech, although work is needed to better establish a color transformation between the two systems. The limiting magnitudes reported below are average values (roughly for a 4 mm diaphragm) and, since broad-band NIR observations are background-limited, will vary with observing aperture. FIRT gives the following choice of filters and diaphragms:
