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A.2.4 Non-continuum images

The existence or absence of continuum flux in an IUE echellogram is determined by the order registration module. Because interorder-overlap flux can affect background determinations only for continuum images, in the noncontinuum case BCKGRD does not go through a Pass 1 step. The background estimates for these images are determined by sampling the interorder background on the long-wavelength side (spatial) of a given order with a one-pixel slit. A 7th degree Chebyshev solution is then computed for this nearly continuous array of interorder pixels. Note that tests show that some minor contamination from strongly saturated emission lines has been detected in neighboring orders.

Figure A.4:   Final background solution for SWP20931, order 95 (smooth solid line). The comb structure connected to the solution reflects the solutions for the various Pass 1 swaths sampled at the line position of this order.

Karen Levay