NEOWISE spectrum 20200716

Forums Comets C/2020 F3 (NEOWISE) NEOWISE spectrum 20200716

Hugh Allen

I captured an Alpy spectrum of the bright coma and adjacent tail on Thursday evening. I removed the sky background from the spectrum but I didn’t attempt to subtract the solar spectrum from sunlight reflected off the dust in the coma. So the sodium emission will be weakened a little by that, but I think only by a very small amount. Compared to spectra taken a week or two ago, the yellow sodium emission certainly has weakened considerably relative to the blue-green C₂ emission bands, hence the subtle change in colour I think. In my comparison it can be seen how the sodium emission persists out into the tail whilst the molecular emission bands fall away in intensity. Visually the tail was huge, extending far from the bright nucleus especially in averted vision – a beautiful sight!