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CCD Format

Figure C.1 shows the CCD format; in particular the position of the imaging area within the data frame. This figure shows the appearance of the CCD as displayed on the Lexidata, which is a mirror image of the actual chip.

The CCD is mounted with its long axis in the dispersion direction. Row 1 is read out first, and appears at the right of the Lexidata screen. Row 1 is the red end of the spectrum.

Columns 1-12 are the `underscan' region of the CCD, that is, it is an area not subject to illumination during an exposure. This region can be used to determine the zero reference level for the data frame. This is typically 123 7 adu.

Columns 13-397, and rows 1-578 are the true image elements of the CCD.

Columns 398-400 and rows 579-590 are the overscan regions. They contain residual signal, the magnitude of which is indicative of poor charge transfer efficiency.

Tue Apr 12 04:13:28 BST 1994