Lorenzo Comolli's Astronomy HomePage

Comet Tsuchinshan was discovered in 2023 by the Chinese observatory of Purple Mountain Observatory, XuYi Station (about 80 km North of the big city of Nanjing), and the US funded ATLAS robotic survey from the South Africa station. Predictions were very good, with a bright display in Sept-Oct of 2024. However the comet was very near to the Sun at the maximum brightness, and not observable except from space from SOHO spacecraft. During the last days of September the comet was observable mainly from the Southern hemishpere, while from ~11 October it was observable from the Northern hemisphere. Here are some of the images that I've captured from my home town in Italy, toghether with some other images captured by my friend Emmanuele Sordini and processed by me. Emmanuele moved to Sicily for a full week during the maximum visibility of the comet because the weather in the Northern Italy was extremely bad, with uninterrupted rain and cloud cover from 12 Oct to 19 Oct included. A very unlucky situation for me!

The comet in October showed only a dust tail, nearly without any coloured features. So we decided to image in black and white using monochrome cameras. This allowed to get the best signal to noise ratio, also especially the comet was extremely low on the horizon, during the twilight, with strong light gradients that I removed during processing so to get the best view of the comet.

An exceptional feature of this comet was the anti-tail, visible at best of 14 October 2024. On that day the Earth crossed the orbital plane of the comet, and so the anti-tail was visible at best. See wikipedia for an explanation of the anti-tail.
The tail length was also quite good, 17° at maximum when imaged from dark and clear sky locations. In our images below the tail is exceeding the field of view of the images, so more than 10°.

Technical Data
Optics	TEC 140
Focal Length	1011 mm
Focal Ratio	f/7.2
Exposure Time	530 x 1 s at 0.66 fps (selection of frames for the processing at top)
CCD	ASI 6200 MM used in software binning 2x2
Chip temperature	0°C
Location	Tradate, VA, Italy, at 305 m height
Date	11 October 2024
Mount	Gemini G41
Temperature and humidity	T=~15°C, RH=~80%
Notes	Centering the comet in the very bright twilight sky was a desperate undertaking. I succeded only thanks to Sharpcap feature of plate solving a nearby field with only 5 stars! Inpressive feature.

Technical Data
Optics	Sigma 150-600 mm
Focal Length	300 mm
Focal Ratio	f/6.3
Exposure Time	129 x 5 s
CCD	ASI 2600 MM
Chip temperature	-10°C
Location	San Fratello, ME, Italy (Sicily, Nebrodi mountains)
Date	13 October 2024
Mount	ZWO AM5
Temperature and humidity	T=~20°C, RH=~60%
Notes	North at left. Processing using Siril with dark, flat, darkflat. Separate processing for stars and comet. Star layer aligned on stars and stars extracted using Starnet. Comet layer aligned on the comet, average with rejection to remove the stars. The very bright gradient due to the twilight low on the horizon was removed.

Technical Data
Optics	Sigma 150-600 mm
Focal Length	150 mm
Focal Ratio	f/6.3
Exposure Time	152 x 10 s
CCD	ASI 2600 MM
Chip temperature	-10°C
Location	San Fratello, ME, Italy (Sicily, Nebrodi mountains)
Date	14 October 2024
Mount	ZWO AM5
Temperature and humidity	T=~20°C, RH=~60%
Notes	North at left. Processing using Siril with dark, flat, darkflat. Separate processing for stars and comet. Star layer aligned on stars and stars extracted using Starnet. Comet layer aligned on the comet, average with rejection to remove the stars. The very bright gradient due to the twilight low on the horizon was removed.

Technical Data
Optics	Sigma 150-600 mm
Focal Length	150 mm
Focal Ratio	f/6.3
Exposure Time	40 x 15 s
CCD	ASI 2600 MM
Chip temperature	-10°C
Location	San Fratello, ME, Italy (Sicily, Nebrodi mountains)
Date	15 October 2024
Mount	ZWO AM5
Temperature and humidity	T=~20°C, RH=~60%
Notes	North at left. Processing using Siril with dark, flat, darkflat. Separate processing for stars and comet. Star layer aligned on stars and stars extracted using Starnet. Comet layer aligned on the comet, average with rejection to remove the stars. The very bright gradient due to the twilight low on the horizon was removed.

Technical Data
Optics	Sigma 150-600 mm
Focal Length	150 mm
Focal Ratio	f/6.3
Exposure Time	30 x 15 s
CCD	ASI 2600 MM
Chip temperature	-10°C
Location	San Fratello, ME, Italy (Sicily, Nebrodi mountains)
Date	16 October 2024
Mount	ZWO AM5
Temperature and humidity	T=~20°C, RH=~60%
Notes	North at left. Processing using Siril with dark, flat, darkflat. Separate processing for stars and comet. Star layer aligned on stars and stars extracted using Starnet. Comet layer aligned on the comet, average with rejection to remove the stars. The very bright gradient due to the twilight low on the horizon was removed.

Technical Data
Optics	Canon 100-400
Focal Length	200 mm
Focal Ratio	f/6.3
Exposure Time	95 x 15 s
CCD	ASI 6200 MM
Chip temperature	-5°C
Location	Tradate, VA, Italy
Date	20 October 2024
Mount	Kenko NES
Temperature and humidity	T=~15°C, RH=~80%
Notes	North at left. Processing using Siril with dark, flat, darkflat. Separate processing for stars and comet. Star layer aligned on stars and stars extracted using Starnet. Comet layer aligned on the comet, average with rejection to remove the stars. The very bright gradient due to the twilight low on the horizon was removed.