2020 Aug 03
: Phil Plait wrote a bit about this in his newsletter: badastronomy.substack.com/p/ban-241-climate-irony-goodbye...
Data originally collected by William C. Keel
on 2020 July 24 using the Jacobus Kapteyn 1m telescope
. He'd already done the work of flat fielding and stacking the exposures in r, v, and b bands, and asked if I'd like to take a shot at processing it further.
At first I was interested in the faint striations already visible in the tail, but later I discovered a kind of spiral emanating from the coma. Initial attempts weren't pretty, and had a lot of introduced artifacts. At some point I realized I could use the same kind of subtraction model I've used in the past for elliptical galaxies to take away excess light in a uniform pattern, which brings out structures that do not match that uniform pattern.
The spiral pattern was most apparent in the b band, mostly visible in the v band, but almost completely gone in the r band. Because of this, I went ahead and used color data from the normal, non-subtracted RVB image, and luminosity from just the model-subtracted b band.
I did use some rather heavy noise reduction in the darker parts of the image, but noise reduction was not necessary for the brighter parts. I tried to make the noise appear uniform. Some small columns of missing data created by a dead or hot pixel were cloned out to the lower right within the coma.
Future reference for self: The curve you need to start with for comets is 1/x (with many thanks to Bill for figuring this out for me)
Pixel scale is 0.34" per pixel
Luminosity: model-subtracted b band
Red: r band
Green: v band
Blue: b band
North is up.