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Mask Design Using GMOS Pre-Imaging

Information about pre-imaging supplied by Gemini

For MOS programs scheduled during the current semester, the PIs will receive separate instructions by e-mail on how to retrieve the reduced and co-added images of their targets from the Gemini Science Archive. Due to the short time available to design and prepare the masks, it is strongly recommended to use these images as the basis for the mask designs, rather than to start from the raw imaging data.

The reduced and co-added images have been produced using the Gemini IRAF package which includes reduction software for GMOS. The software correctly takes into account the gaps between the CCDs and the misalignment of the CCDs relative to each other.

The images have been co-added with the task imcoadd, which is also part of the Gemini IRAF package. The co-added images are average images, thus they are scaled to the exposure time of the individual images used to create the co-added image (see the keyword EXPTIME in the header of the primary header unit). Further, the co-added images are in e-/pixel.

For images taken under photometric conditions, an approximate standard calibration is supplied.