We discuss the instrumental and data reduction techniques used to suppress speckle noise with the Simultaneous Differential Imager ( SDI ) implemented at the VLT and the MMT .
SDI uses a double Wollaston prism and a quad filter to take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 \mu m 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 significantly attenuated , resulting in photon noise limited data past 0.5 ” .
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 survey of nearby young stars at the VLT and MMT ( see Biller et al. , this conference ) , we achieved H band contrasts > 25000 ( 5 \sigma \Delta F1 ( 1.575 \mu m ) > 10.0 mag , \Delta H > 11.5 mag for a T6 spectral type object ) at a separation of 0.5 ” from the primary star .
We believe that our SDI images are among the highest contrast astronomical images ever made from ground or space for methane rich companions .