Lhires IR thread refreshed

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Kevin Gurney

Greetings to all in these strange and difficult times… I hope you are keeping safe.

Anyway, I am looking again at the instrument response in my Lhires data. I have a  ‘hockey stick’ response with an uptick at the extreme red end (centred on Ha). In the raw spectrum there is a spreading of the line here but, of itself, I dont  see  that it implies a greater binned amplitude.

As Robin suggested earlier in this thread, I looked at using the UVES stars for reference. I  attach a couple of plots showing results for castor and regulus. Each plot shows (i) the non-IR corrected spectrum; (ii) the use of the star’s own IR obtained using the reference in the ISIS database; (iii) the IR from the other star of the pair.

On the one hand, the ‘uptick’ in response at the extreme red end is removed somewhat, in both IR-corrected cases. On the other hand, the corrceted responses differ considerably. Reassuringly, the IR for each star is fairly independent of camera binning (1×1 and 2×2 give good agreemenet for each star) so I think the IRs have been processed OK.

On balance therefore, I am inclined to agree with Andrew, that using IRs in these high-res spectra may introduce other artefacts in an unrelaible way.

Robin, I also  note that, in some of your Lhires examples, you crop at around 6612A. I have started to so this too, so the worst of the uptick is discarded.

I would have thought that, as long as it’s clear what you do (I uncheck the IR box on the dbase entry, and insert appropriate comments in the header) its OK to use an uncorrected spectrum?

Keep safe