QC PLOTS
	CURRENT	HISTORY
X0 and Y0
matrix coefficients
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The Mask to CCD Transformation Matrix translates mask coordinates into CCD pixels. It is determined with special MOS masks having pinholes on a regular grid. Measurements using these mask are typically executed once a day for health check purposes.

Example MOS pinhole mask image

The transformation matrix has the following form:

X = a_xx * x + a_xy * y + x_0
Y = a_yx * x + a_yy * y + y_0

with (x,y) being mask coordinates in mm and (X,Y) CCD coordinates in pixels. X direction is along the slit orientation, y direction is perpendicular to the slits (i.e. in dispersion direction).

The matrix coefficients a_xx, etc. and the zeropoints x_0 and y_0 are determined from the pinhole image for each quadrant. The diagonal coefficients a_xx and a_yy give the scale factor between mask and CCD (around 8.4 pixels/mm). The coefficients a_xy and a_yx give the rotation and are nearly zero.

QC1 parameters

<(Here you should provide information on QC1 parameters - possibly also some which are not trended - that goes beyond the information provided on the Daily Health Check Pages and the QC1 Database. You could provide it in a table, like in this example, or in a list) >