Data Reduction Frequently Asked Questions
I've had some trouble extracting a good RV value through EsoReflex for some spectra. A quick look at the CCF shows no line, or a line with different properties than expected, while a quick glance at the spectrum suggests it looks reasonable. Any idea what is going on here and how to fix this?
Please check rv_centre, rv_range, and rv_step parameters. In particular, if the RV of the star is outside the -20+20 km/s boundary, as happens with so many stars, the CCF computation will not show the average line of the spectrum. Following this, the pipeline cannot find the "true" minimum/maximum, and just picks the minimum value in the range. rv_range has to be large enough for the pipeline to be able to locate the minimum/maximum that corresponds to the center of the line.