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A cross section through the coma using the same technique as for 2020 F3 NEOWISE
https://britastro.org/jbaa/pdf_cut/jbaa_24438.pdf
fig 4a
The most obvious differences are that sodium emission is absent and the C2 distribution in 2020 R4 is similar to that of CN, broader than in 2020 F3
Cheers
Robin
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Robin. A pretty neat article. Around the time when the comet was visible night and morning, I took a mixture of images on a Star Adventurer with a 300 mm lens. On some of the wide angle images with the standard 18-55 mm lens, I used a diffraction grating. I didn’t do anything with the images at the time, but meant to go back one day. The magnification with a wide angle is quite small though. Although the tail came out very bright and sky had a glow to it, I’m not sure if there was any faint diffraction pattern. I should go back and check in negative format. That was the night my car battery failed when I was out in the countryside and I didn’t know my location 🙁
Hi Derek,
What date was this ? Objective grating setups showed a nice little sodium coma and tail.
My early example on 7th July
https://britastro.org/comment/8806#comment-8806
and a better one a few days later by Mike Harlow
https://britastro.org/comment/8832#comment-8832
but the sodium dropped in intensity after that and was lost in low resolution spectra around 22nd July
Cheers
Robin
The spectrum of the central coma is now on my BAA observer’s page here
Hi Robin
This image was taken on 12th July where I went out. But I will have some others around that date. I will check. But I think I only tried the diffraction grating on 12th until it misted up then reverted to without grating.
I can’t be sure of the orientation of the lines now, and at the time, I was puzzled by the lack of obvious spectra from some of the brightest stars (unless they were out of field).
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