ISAAC filter wheel

The ISAAC instrument filter wheel. ISAAC is an infrared (1 - 5 μm) imager and spectrograph mounted on the Nasmyth B focus of the VLT UT1. It has two independent arms, one equipped with a 1024 x 1024 Hawaii Rockwell array and the other with a 1024 x 1024 InSb Aladdin array from Santa Barbara Research Center. The Hawaii arm is used at short wavelengths (1 - 2.5 μm). The Aladdin arm is used predominantly at long wavelengths (3 - 5 μm) but is also available for short wavelength imaging with broad band filters.