Comet Section        


August 5, 2021 – ALPO Comet News for August 2021


July saw the discovery of 9th magnitude C/2021 O1 (Nishimura), though the comet was located so close to the Sun that few have been able to observe it. While we are still waiting for a comet to brighten into an easy-to-observe object for small apertures, a number of fainter comets are visible in the magnitude 10-13 range for imagers and large aperture visual observers. A recent discovery, C/2021 O3 (PANSTARRS), is currently around 18-19th magnitude but may brighten into a nice binocular object early next year.

Comets Section News

The ALPO’s Annual Conference will be held virtually on Friday and Saturday, August 13-14. Each day is packed with talks about various aspects of Solar System observing. The Comets Section will be presenting two talks. One will be an overview of the past year’s comet observations. The second talk will be on a slightly different topic, Solar System numismatics (i.e., Solar System objects, including comets, on coins and medals). The meeting is free and more information on the conference and how to watch can be found on the ALPO web site at

During July, the ALPO Comets Section received 27 images and/or sketches from Michel Deconinck, Carl Hergenrother, Martin, Mobberley, and Mike Olason of the following comets: 4P/Faye, 7P/Pons-Winnecke, 10P/Tempel, 15P/Finlay, 19P/Borrelly, 47P/Ashbrook-Jackson, 106P/Schuster, C/2017 K2 (PANSTARRS), C/2017 Y2 (PANSTARRS), C/2018 U1 (Lemmon), C/2019 K7 (Smith), C/2019 T3 (ATLAS), C/2019 T4 (ATLAS), C/2019 U5 (PANSTARRS), C/2020 F2 (ATLAS), C/2020 H5 (Robinson), C/2020 K1 (PANSTARRS), C/2020 M5 (ATLAS), C/2020 O2 (Amaral), C/2020 PV6 (PANSTARRS), C/2020 T2 (Palomar), C/2021 A1 (Leonard), C/2021 O1 (Nishimura).

The Section also received 82 visual and CCD magnitude measurements from Michel Deconinck, J. J. Gonzalez, Carl Hergenrother, Mike Olason, and Chris Wyatt of comets 4P/Faye, 7P/Pons-Winnecke, 10P/Tempel, 15P/Finlay, 19P/Borrelly, 67P/Churyumov-Gerasimenko, 106P/Schuster, 246P/NEAT, C/2017 K2 (PANSTARRS), C/2018 U1 (Lemmon), C/2019 F1 (ATLAS-Africano), C/2019 L3 (ATLAS), C/2019 T4 (ATLAS), C/2020 F5 (MASTER), C/2020 J1 (SONEAR), C/2020 PV6 (PANSTARRS), C/2020 T2 (Palomar), C/2021 A1 (Leonard), and C/2021 O1 (Nishimura).

In addition to observations submitted to the ALPO, we also occasionally use data from other sources to augment our analysis. We acknowledge with thanks comet observations submitted to the International Comet Quarterly, Minor Planet Center, COBS Comet Observation Database, and our own ALPO contributors used in this report.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

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