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MASTER_FLATs L(ower) and U(pper CCD), with the echelle orders slightly inclined from left to right. The central white boxes (100x300 pixels wide) mark the windows used for the statistical analysis. |
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Closeup of masters L and U, with the pixels from the analysis boxes extracted. Horizontal axis is dispersion (X), vertical axis is slit coordinate, Y. 3 (2) orders are fully visible. The inclined dark strips are part of the slit function. |
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Difference frames of the first two raw frames used
for creating the MASTER_FLATs. Differences in pixel intensity are
purely statistical (photon noise). The black interorder areas have
been masked to avoid contribution to the statistical analysis. Orientation of all raw frames is rotated by 90 degrees. |
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X-derivative frames. The first raw frame of the stack has been shifted in X by 1 px and subtracted. The result frames (for U and L areas) show any structure in X (dispersion) direction enhanced. Here a few 'hot' pixels with strongly deviating gain (may also be small dust particles) become visible in the L frame. The U frame shows some extended structure which may be faint fringing. Gain fluctuations are randomized. Interorder space is masked to not contribute to the resulting std dev. |
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Y-derivative frames. The first raw frame of the stack has been shifted in Y by 1 px and subtracted. The result frames (for U and L areas) show the Y-structure enhanced. Both L and U frames show the slit function very clearly. This is due to the narrow slit (0.3"). Interorder space is masked. |