Extraction

The extraction consists in the summing up of the spectral pixels along the spatial direction into a final onedimensional spectrum (one per aperture or optical fibre). We can do the extraction of the apertures with the standard widths and the previously determined tracing polynomial using apall (see Appendix I).

After the extraction, we have 2D-image of n$\times$m dimensions, where n is the number of pixels along the dispersion axis and m the number of fibres.