Data Reduction Frequently Asked Questions
On the MERGE2D spectrum I see blobs with intensity zero. Why?
During resampling the pipeline uses a CPL routine which returns a parameter to indicate the confidence for the resampled pixel intensity. If the area used for resampling contains at least one pixel flagged as bad the pipeline flags the resulting resampled pixel as "MISSING DATA" (using code 524288), and sets the pixel flux to zero. This behaviour is currently mostly seen for BSPLINE sky subtraction where sky line residuals are flagged.