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A dedicated code designed to simulate observations made with a high contrast imaging instrument using an integral field spectrograph and an extreme adaptive optics system (CHEOPS) is in progress. High contrast and high angular resolution are required in order to detect close faint companions and exo-planets using the differential technique. In this paper we present a comparison, made in order to validate the code, between simulations and observations recently obtained with the Simultaneous Differential Technique (SDI)\cite{len03}, an up-graded version of NACO (AO facility at the ESO-VLT 8m telescope "Yepun").

We discuss data reduction techniques and results from the Simultaneous Differential Imager (SDI) implemented at the VLT (Lenzen et al. 2004a) and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 μm methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be attenuated by a factor of >102. Non-trivial data reduction tools are necessary to pipeline the simultaneous differential imaging. Here we discuss a custom algorithm implemented in IDL to perform this reduction. The script performs basic data reduction tasks but also precisely aligns images taken in each of the filters using a custom shift and subtract routine. In our commissioning runs at the VLT and MMT, we achieved contrasts up to a factor of 45000 (ΔH=11.7) at a separation of 0.6" from the primary star. With this degree of attenuation, we should be able to image a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We believe that our SDI images are the highest contrast astronomical images ever made from ground or space.