(most of) the object signal and create a fringe/sky residual template for each slit. Subtracting this from the frames resulted in an improved signal-to-noise ratio for the object spectra. Depending on the seeing conditions and the dithering offsets used, not all object signal was perfectly removed, thus the extracted spectra significantly underestimated the real spectra. As our primary goal was object identification, not spectrophotometry, this was an acceptable trade-off.

*Coadding the Frames*
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After sky subtraction, all the slits were visually inspected to verify that the object is indeed in the ’good’ region of the slit. This step was necessary since the applied small spatial offsets between the science exposures can result in objects falling too close to the slit edge (MOS blade corners are round, thus the slit is not usable there) or falling completely outside the slit.

After this visual screening, the [*spatial*]{} offset between different exposures of the same object was caculated based on the [*world coordinate system*]{} (WCS) information stored in the frame headers. The individual exposures were coadded (including the rejection of suspicious pixels or cosmic ray hits) after applying these spatial shifts. We only shifted the frames in the spatial direction and only by 