The Comet's Tale
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1 The “Book of Miracles” includes 26 examples of comets, including this one: “In the year 1007 A.D., a wondrous comet appeared. It gave off fire and flames in all directions. As it fell to Earth it was seen in Germany and Italy. Augsburg Book of Miraculous Signs THE COMET’S TALE Comet Section – British Astronomical Association Journal – Number 40 2021 July britastro.org/comet C/2020 R4 (ATLAS). 2021 May 8, 0600 UT by Dan Bartlett, June Lake, California USA (North left) 2 Table of Contents Contents Author Page 1 From the Director Nick James 3 Section Director 2 MISSION 29P Help Richard Miles 7 Needed! 3 Spectroscopic Robin Leadbetter 10 Observations of Sodium in C/2020 F3 (NEOWISE) 4 Video Astrometry of Alex Pratt 15 Comets 5 Estimating Coma Nick James 23 Diameter Using Comphot 6 Observing Comets in José Guilherme de Souza 27 Brazil Aguiar 7 My Remote Peter Carson 31 Observatory for Comet Observing 8 My First Comet Tim Printy 35 9 Comet 12P/Pons- Neil Norman 39 Brooks 10 The Schwassmann- Denis Buczynski 44 Wachmann Comets: A review 11 The Comet Section Nick James 51 Image Archive Contacts 56 Picture Gallery Please note that copyright 57 of all images belongs with the Observer Frontispiece Image by Dan Bartlett Celestron RASA 11" (0.28-m, f/2.2 Rowe-Ackermann Schmidt Astrograph), ZWO ASI294MC Pro, 10MICRON GM2000 HPS mount. Software: Pleiades Astrophoto, S.L. PinInsight 1.8 Sequence Generator SGPro. Date: 2021 May 8, 06:00 UT Focal length: 0.62-m, Seeing: 4, Transparency: 8. https://britastro.org/cometobs/2020r4/2020r4_20210507_dbartlett.html 3 1 From the Director – Nick James Another year has passed and another issue which are relevant to comets. I’ve listed of the Comet’s Tale has arrived. What a these at the end of this editorial. No matter very strange year it has been. The Covid how good virtual meetings are they can’t pandemic has changed many aspects of our replace face-to-face meetings and I’ve lives and things that we took for granted really had enough of Zoom, Webex, Skype were no longer allowed. Within the BAA and all the rest. I hope that we can get back we have not held a physical meeting since to a more normal life soon. In particular I 2020 February and I really do miss them. would like to organise a physical Comet As a replacement the BAA implemented a Section meeting sometime in the spring of set of webinars which have been well 2022. If you have any suggestions for a received. These are available to watch on venue, please let me know. YouTube and there have been a number From an astronomical point of view 2020 hemisphere morning object after its July 3rd was a good year. We had an excellent run perihelion. My first view of it was on the of good observing weather in the late July 6 and it was far brighter than I had spring and the Covid restrictions meant expected. Over the following few weeks, it that there were far fewer aircraft in the sky blossomed into a mini-Hale-Bopp with a with a consequent reduction in man-made wide, curving, structured dust tail and a cirrus cloud. We also had one, very nice, very long, blue ion tail. It was so exciting to comet. have a naked eye comet in the sky. My best night was Friday 10/11 July when it was Of course, a year ago we had no idea that clear from dusk to dawn. The comet was a C/2020 F3 (NEOWISE) was going to turn beautiful sight in the peaceful, deep blue, out to be the impressive object it was. The midsummer twilight and it was joined by a comet had been discovered in late 2020 very active noctilucent cloud display on the March as a southern hemisphere object and northern horizon. it finally emerged as a northern 4 The Section received a huge number of those of us who thought it was a really excellent images of this comet, all of which prominent object, a lot of people couldn’t are lodged in the section online archive. find it. I expect that many people really Thank you to everyone who sent in had no idea what they were looking for and material. I am currently working on a full probably expected to see something as paper for the JBAA but, in the meantime, I prominent as the views in images. Local wrote a summary which appeared in the light pollution is a problem for many as 2020 October edition. well. https://britastro.org/system/files/jbaa_pd Over the last year we’ve also had some f/v130i05j_0.pdf very exciting observations of 29P/Schwassmann-Wachmann, the huge This was one of the brightest comets we Centaur comet that orbits outside the path have seen from the northern hemisphere in of Jupiter. Richard Miles runs the Mission the last couple of decades and quite a few 29P programme for the section and many non-astronomer friends commented that observers now have this object high on they had seen it. Surprisingly though, for their list of priority targets. The comet has 5 fairly frequent small outbursts and a few fast so I reported the outburst to the larger ones each year. On 2020 November section mailing list at 18:58. Many 19 I started observing after getting home observers managed to catch this outburst from work and got my first image at 18:46 but the most impressive sequence was UT. On examination it showed the comet at from Jean-François Soulier. He has an magnitude 14.5, two magnitudes brighter automated 0.20-m telescope which than the previous night. I emailed Denis monitors the comet continuously and he Buczynski and Richard and, a few minutes caught the entire outburst. These later, Denis responded that he had observations show that the outburst observed the comet at 18:02 when it was started around 25 minutes before my first magnitude 16.2. I initially thought that I image. The outburst lightcurve that must have made a mistake so I checked for Richard generated from his observations is field stars but there were none. As the extraordinary and it shows how rapidly the images were appearing on screen it was comet brightens. obvious that the comet was brightening Many thanks to all the observers who and it is very well placed for those of us in continue to contribute to this important the UK. We also have C/2020 T2 (Palomar) programme. The comet is in conjunction at which has been brightening recently and the moment but if you are interested in has taken over from C/2020 R4 as the joining the 29P project please have a look brightest comet in our skies. In terms of at the webpage here: future prospects C/2021 A1 (Leonard) https://britastro.org/node/25120 might become a naked eye object in the Brightish comets are a bit thin on the morning sky in late November but it is too ground at the moment although C/2020 R4 early to tell. (ATLAS) has been around 10th magnitude 6 I hope you enjoy reading this issue. Many former Director, Jonathan Shanklin, who thanks to our editor, Janice McClean, for continues to perform detailed analyses of putting it all together and to Denis cometary activity. There is plenty of Buczynski who has collected a lot of the material in this edition. I hope that you contributions. My thanks also to the find something that will interest you and section committee for supporting me that you will be encouraged to go out and through the year, and particularly to our observe these fascinating objects. Nick James Section Director BAA comet-themed webinars C/2019 Y4 (ATLAS) - https://www.youtube.com/watch?v=N2d_t_fDndo C/2020 F3 (NEOWISE) https://www.youtube.com/watch?v=G6xlpvxJTYQ 29P/Schwassmann-Wachmann - https://www.youtube.com/watch?v=oZciIMau3_4 The Comet Section archive: https://www.youtube.com/watch?v=JgaJ_NRv-uI 7 2 MISSION 29P Help Needed! Richard Miles Nowadays, as well as being a dedicated the region of sky close to the Sun. Michael observer there are other avenues that folk Mattiazzo comes to mind in this respect, interested in Science and Astronomy can his latest success of which was Comet explore: one of which is Citizen Science. C/2021 D1 (SWAN) first found on February This type of investigation is where there 19 of this year. Well done, Michael! are large amounts of data available via the Web and software is provided whereby Discovering comets is one activity but not anyone with a keen interest in the subject one with any guarantee of success these and a suitable computer, can become days. Instead, as members of the BAA involved with relatively little effort. Comet Section, we are also interested in better understanding the nature of comets Take the 'Zooniverse' initiative. They have and in this vein, we have launched a project a number of space-related projects but to study one particular comet in much nothing specifically on comets since these greater detail namely, Comet do not lend themselves to making a quick 29P/Schwassmann Wachmann 1. discovery or two. However quite a few amateurs have discovered new comets by Entitled ‘MISSION 29P’ the details can be looking for interlopers in SWAN imaging of found on a dedicated webpage: 8 https://britastro.org/node/25120 2. After the comet has outburst, we often Nick James and I would like to enlist the see an asymmetric coma developing help of a few people to analyse images of sometimes having the 'Pac-Man' ᗧ shape.