Data Reduction Frequently Asked Questions

I get inconsistent results from different absorption/emission lines in my NIR spectrum - why?


The NIR detector is read in a way that flux is extrapolated once it leaves the normal regime. This is no problem as long as observing conditions stay constant. If for instance the transparency varies a linear extrapolation will no longer give correct results. You can find pixels which have extrapolated flux by looking for the value 1048576 or larger in the QUAL extension. Adding this number to the decode-bp parameter will cause these pixels to be treated as bad. For more details see this report.