I don't think there's any evidence of the Na emission, but maybe the Sun is to low at that time?
Lars, I don't understand if you refer to telluric sodium that, being an emission source over the entire field, is undetectable with slitless spectroscope like SA100.
Another topic we are discussing on Staranalyser Y group is the sodium tail image, well visible in Rob Kaufman SA100 spectrum (from Australia) but not appreciable in Lars spectra. For this I suppose is due to much larger comet image and a decreased sodium emission. Concerning the last aspect, Robin suggests to measure EW that I find a -50 value on my Lhires III spectrum of 16 march, normalizing on continuum around peak. I don't know if it's correct, should I normalize on the sky background?
Ciao
Paolo