Makee: Echelle Order Trace Plots
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.
What to look for:
Here is an example of a "typical" good set of trace fits for a image with
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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