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MASTER_FLAT, with the echelle orders slightly inclined from left to right. The central white box (100x100 pixels wide) marks the window used for the following statistical analysis. |
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Closeup, with the white analysis box |
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Difference frame of the first two raw frames used
for creating the MASTER_FLAT. Differences in pixel intensity are purely
statistical (photon noise). The black area has been masked to avoid
its contribution to the statistical analysis. Orientation of all raw frames is rotated by 90 degrees. |
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X-derivative frame. The first raw frame has been shifted in X by 1 px and subtracted. The result frame shows any structure in X direction (dispersion) enhanced. Here a column with strongly deviating gain becomes visible. Gain fluctuations are randomized. Interorder space is masked to not contribute to the resulting std dev. |
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Y-derivative frame. The first raw frame has been shifted in Y (slit direction) by 1 px and subtracted. The result frame shows the Y-structure enhanced. A row with strongly deviating gain becomes visible, as well as some very faint slit structure (two dark stripes inclined with the orders). Interorder space is masked. |