Image Details
Caption: Figure 5.
The measured locations of the dither offsets derived from all continuum sources in fields observed between January 1 and 2020 June 30. The large black, blue, and red circles represent the size of a fiber and the assumed position in the standard three-point dither. The black, red, and blue points are the measured positions for dithers 1, 2, and 3, respectively, where we have centered the three dithers on their average position. The light green crosses show the centroids of dithers 2 and 3, while the light green squares illustrate the desired center; the offset between these positions is likely due to a small difference in plate scale. For HETDEX reductions, it is not important that the commanded and actual dither positions match, but it is critical that we know what the actual dither position is. After accounting for an overall scale factor, the measured offsets are consistent with the requested centers, and the measured scatter of the dither centers is the same as our measurement accuracy. This agreement allows us to use the requested dither offsets in our data reduction; the measured dither positions are only used as a check on the data.
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