Comet 103P/Hartley 2

"Comet Hartley 2, designated as 103P/Hartley by the Minor Planet Center, is a small periodic comet with an orbital period of 6.48 years. It was discovered by Malcolm Hartley in 1986 at the Schmidt Telescope Unit, Siding Spring Observatory, Australia."

"Hartley 2 was the target of a flyby of the Deep Impact spacecraft, as part of the EPOXI mission, on 4 November 2010, which was able to approach within 700 kilometers (430 mi) of Hartley 2 as part of its extended mission. As of November 2010 Hartley 2 is the smallest comet which has been visited and the fifth comet visited by spacecraft, and the second comet visited by the Deep Impact spacecraft" https://en.wikipedia.org/wiki/103P/Hartley

"...the comet nucleus to have a radius of 0.57 ± 0.08 kilometers (0.354 ± 0.050 mi) and a low albedo of 0.028. The mass of the comet is estimated to be about 300 megatonnes (3.0×1011 kg)...the comet should be able to survive up to another 100 apparitions (~700 years) at its current rate of mass loss."

"Hartley 2 is a hyperactive little comet, spewing out more water than other comets its size", "When warmed by the Sun, dry ice [frozen carbon dioxide] deep in the comet's body turns to gas jetting off the comet and dragging water ice with it."  Michael A'Hearn, lead author on the Science paper and principal investigator for the EPOXI and Deep Impact missions.

Observations of Hartley 2 by the Deep Impact spacecraft showed the importance of carbon-dioxide ice relative to carbon-monoxide ice in comets, and led to reexamination of all previous observations of these two ices in comets. The relative abundances in short-period and long-period comets imply that the short-period comets formed under warmer conditions than did the long-period comets. Thus, the short-period comets must have formed closer to the sun than their longer-period brethren. This is contrary to popular belief in the astronomical community (for many decades) that the short-period comets formed in the Kuiper belt beyond Neptune, while the long-period comets formed in the vicinity of the giant planets. The new model fits well with measurements by other astronomers of heavy water in Hartley 2, and with the newest dynamical studies of planetary migration.  https://www.jpl.nasa.gov/news/nasas-deep-impact-produced-deep-results

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This is the second comet Maurizio could image this year.
Back in October during a working week in San Costantino Albanese South of Italy, Maurizio took the opportunity to image the comet in a Bortle 4 zone at almost 1000masl.  Maurizio told me that was very hard to find the comet as was very faint.

The session was 76 frames  x  30'' at ISO 1600.

I was processing a nebulae when Maurizio give to me this data so I decide to test the last version of DSS 5.1.5  I was using with nice perfomance and resut in the nebulae see if I had same luck with the comet as I know have some issue in the past with this kind of target process. The comet signal in the frames are really really faint.  The normal stack (for get the base stars) give a nice result with a clear strike of the comet as usual. For the comet stack only position, I do not know if was due for the really faint comet signal, and  even doing several attempts all of them given to me a comet stack only with a very short but noted strike not pinpoint comet head. I redo each time the position in the first, middle and last sequential frame.

Then I used Siril doing the workflow of stacked comet with background extraction and comet only without stars (using Starnet2) and I got pinpoint stack of the comet head.  Then I combined this result in PS with the layer of only stars from Siril and DSS. On CamRaw I apply a slight white, clear, dehaze and noise reduction with denoise Topaz  in the only comet layer for get the final image.

The image was slightly cropped and saved at 125%.

As in the sky around the comet I saw few and very little galaxies I try to track them in Simbad and are the annotated in the image. (seems the PI sky plot of Astrobin did some of them too ).

Using part of the workflow done in Siril, I did a clip of the comet you can see in the revision B and C.

We hope you had a lovely Merry Christmas and we wish you a serene New Year 2024, health and full of new stellar adventures.

Clear Skies and thanks for your visit.

Nicla and Maurizio