Comet NEOWISE C/2020 F3

Comet NEOWISE has been the naked eye comet that many astronomers have been eagerly awaited for years. It has been a month long marathon of observations and nights out.

July 6th 2020 morning

my first imaging of comet NEOWISE, with Maksutov Newton telescope, to be processed

July 7th 2020 morning

be processed, with Maksutov Newton telescope, red “sodium” tail visible on picture, no ion tail

July 8th 2020 morning

NEOWISE with noctilucent clouds! more images to be processed

July 11th 2020 morning

NEOWISE with “sodium” tail and ion tail at 200mm focal length. Good data set, the sodium tail is wider than on the 12th of July. To be processed.

observation with 100mm binoculars.

July 12th 2020, morning

Excellent set of images. The observation was made from the Northern coast of Finistère with the comet above the ocean, and absolutely no light pollution. The view was just spectacular to the eye, and with the 100mm binoculars.

The image reveals the complex tail structure of the comet: a large, fanned dust tail with beautiful synchronic striation, the blue ion tail tails with blue gaseous wisps, and the rare red “sodium” tail.

If you are not familiar with the anatomy of comets, below is a labeled image to help identifying the main features of the comet

The image is made with the 70mm-200mm focal length zoom, set at 200mm and at aperture of f/2.8. Altogether, the total exposure is a bit less than 1 hour. In order to avoid blur due to the motion of the fine structures within the tails, a special registration on the details of the tails was made. It allowed to keep all the finest details visible. Being able to obtain images with stars subtracted well enough to allow to register on the tail structures is clearly the most difficult part of the processing.

The excellent signal to noise ratio of the images with zero light pollution interference allows to reveal unusual, discrete features, like the ion tail beneath the dust tail, color variations of the dust tail with larger dust, located on the bottom edge of dust tail being slightly redder, or the green C2 coma signature visible very near the nucleus. Even color variations within the synchronic bands structure seems visible on the enhanced color image below.

In order to help seeing the structure of the different, overlapped, tail components, I did some color subtraction to help distinguish the different tails. Such channel subtraction increases the noise, but with the very good signal to noise ratio of the data, it is possible to isolate meanignfully the different components of the comet using this technique.

  • Subtracting the blue channel from the signal of the “sodium” tail (Red and Green channels) allows to show the actual structure of the sodium tail: a straight and mostly featureless tail, extending up to the edge of the frame.
  • Subtracting the mostly white dust tail from the ion tail signal reveals the ion tail even beneath the brighter dust tail. The ion tail comes from the right hand side of the nucleus mostly on this day. This subtraction also shows that the upper part of the dust tail is bluer, as well as possibly two different dust populations organized in syndynes.
  • Subtracting both the white dust tail and the ion tail from the Red channel isolates the “sodium” tail. It shows that, contrary to the ion tail that comes mostly from the right hand side of the nucleus, the “sodium” tail comes straight at the back of the nucleus. The fact that the two tails do not seem to come from exactly the same area probably explains why, on this day, the two tails only partially overlapped, which help in distinguishing individually both of them.
  • Eventually, subtracting the dust tail from the Green channel in the inner area reveals a green coma around the nucleus hidden beneath the bright dust tail.

Analysis of the color signal of the comet to reveal independently the different components of the comet (open in high resolution here).

July 13th 2020 morning

NEOWISE with sodium tail and ion tail at multiple focal lengths. Excellent data set, the sodium tail is seems to have multiple streamers. To be processed.

Comparison of tails, July 11th, 12th, and 13th 2020

Even though the data from the 11th and 13th of July are not processed with optimal workflow, the differences in the structure of the tails is already worth having a look before the data are fully processed. Here is a link to the comparison image in larger size.

On the 11th of July, the sodium tail is quite broad, with a rather sharp left hand side edge, and a soft right hand side edge. The ion tail shows a main streamer coming from the right hand side of the nucleus and another streamer coming from the left hand side of the nucleus.

On the 12th of July, the sodium tail is quite narrow, an appears as a single streamer, quite well defined. The ion tail comes mostly from the right hand side of the nucleus.

On the 13th of July, the sodium seems to show two separate streamers, coming from both side of the nucleus. Although the ion tail seems to come mostly from the right hand side of the nucleus, it is notably more divergent than the previous days and thus broader.

One can also see the whole dust tail, and its synchrone structures expanding to the right from one day to the other.

July 19th 2020 evening

NEOWISE at 50mm focal length, with very long ion tail

July 22th 2020 evening

NEOWISE at 14mm focal length, bad choice of focal of focal length, image would have been better with 35mm focal length

July 28th 2020 evening

NEOWISE with Maksutov Newton telescope

July 30th 2020 evening

NEOWISE with Maksutov Newton telescope

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