This is an interesting but non-impressive view of comet 46P/Wirtanen in the UV passband of the CN, "Cyanogen" emission line around 388nm. I was hoping to capture some detail in the CN emission, but it is very faint and the camera/optics are not optimized for UV sensitivity.
This is 5x10m exposures oag guided using MetaGuide shift guiding. Shift guiding was essential here for the 10m exposures since the comet is moving so fast.
It is often said that the green color of comets is due to cyanogen - but that is incorrect and the green is due mostly to diatomic carbon, C2, emission. "Cyanogen" or CN is often present, but emits mostly in the UV around 388nm and not in the green.
Details can be found here:
https://www.cloudynights.com/topic/406505-green-in-comets-is-not-cn-cyanogen/Recently images of rotation in this comet were obtained in the CN band as reported here:
http://wirtanen.astro.umd.edu/46P/46P_status.shtmlThe rotation period is about 8 hours and can be observed with professional equipment but I was unable to detect it either with Sloan or CN filters.
I have imaged other comets with a CN filter as shown here:
https://www.cloudynights.com/topic/488373-comet-lovejoy-in-narrowband-c2cn-bicolor-image/but that was with a 300 f/4 dlsr lens - and this image of 46P is with EdgeHD11 at f/7 and 0.4" per pixel.
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