The trace plots show the polynomial fits to position of the centroid of the object on the CCD. It gives the row position as a function of column position. Note that the 0th and 1st order coeffecients of the polynomial fit are subtracted before being plotted. Note that the endpoints of the curves shown are always at 0 on the vertical scale. The measured centroids are shown as dots in each graph. Only every 5th column position is actually plotted.

These fits use the "star" image input to makee (the 2nd command line entry), so to find the trace fit used for a given object look for a file "trace-###.ps" where "###" is the observation number of the "star" image.

Here is an example of a "typical" good set of trace fits for a image with 30 orders: trace-example.ps . On a successful fit the curve should generally follow the centroid points with no deviations larger than about 0.2 pixels between the center of the point scatter cloud and the fitted curve. The accuracy of trace fit is usually within about 0.05 pixels.

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