After the excitement of C/2023 P1 (Nishimura) last month, you might think October will be a little less eventful for comet watchers. While it is true that October won’t deliver a 2nd to 4th magnitude comet like Nishimura was its brightest, there are a large number of comets expected to be brighter than 10th magnitude.

Short-period comets 2P/Encke and 103P/Hartley will be nice 7th to 8th magnitude objects in the morning sky. C/2023 H2 (Lemmon) is a bit of a wild card but could rival Encke and Hartley this month. One of next year’s highlights is in the news again as 12P/Pons-Brooks has experienced yet another multi-magnitude outburst, though whether it will be brighter than 11th magnitude this month is still to be seen.

Last month the ALPO Comets Section received 244 observations of comets C/2023 P1 (Nishimura), C/2023 H2 (Lemmon), C/2023 E1 (ATLAS), C/2022 JK5 (PANSTARRS), C/2022 A2 (PANSTARRS), C/2021 X1 (Maury-Attard), C/2021 T4 (Lemmon), C/2021 S3 (PANSTARRS), C/2020 V2 (ZTF), C/2020 K1 (PANSTARRS), C/2017 K2 (PANSTARRS), 311P/PANSTARRS, 237P/LINEAR, 202P/Scotti, 126P/IRAS, 103P/Hartley, 30P/Reinmuth, 29P/Schwassmann-Wachmann, 13P/Olbers, 12P/Pons-Brooks, 2P/Encke. A big thanks to our August contributors: Dan Bartlett, Michel Besson, Denis Buczynski, Dan Crowson, Jose Guilherme de Souza Aguiar, Michel Deconinck, J. J. Gonzalez Suarez, Christian Harder, Scott Harrington, Carl Hergenrother, Eliot Herman, Michael Jäger, John Maikner, Gianluca Masi, Martin Mobberley, Mike Olason, Uwe Pilz, Ludovic Prebet, Michael Rosolina, Greg Ruppel, Chris Schur, Tenho Tuomi, and Chris Wyatt.

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.

August was a busy month for comet watchers. In addition to observing 12P/Pons-Brooks in outburst and 9th magnitude C/2023 E1 (ATLAS) and C/2020 V2 (ZTF), a new bright amateur comet was discovered around mid-month. C/2023 P1 (Nishimura) is now 6th magnitude and should brighten to 4th-5th magnitude before being lost in the glare of the Sun. September will also see returning periodic comets 2P/Encke and 103P/Hartley brighten to 9th and 7th magnitude by the end of the month, respectively. 

Also, observable in September are C/2020 V2 (ZTF) at 9th magnitude, 12P/Pons-Brooks and C/2017 K2 (PANSTARRS) at 11th mag, C/2021 S3 (PANSTARRS) brightening from 12th to 11th magnitude, C/2021 T4 (Lemmon) fading from 10th to 11th magnitude, and C/2023 E1 (ATLAS) fading from 10th to 12th magnitude.

Last month the ALPO Comets Section received 277 observations of comets C/2023 P1 (Nishimura), C/2023 E1 (ATLAS), C/2023 A3 (Tsuchishan-ATLAS), C/2022 W3 (Leonard), C/2022 JK5 (PANSTARRS), C/2022 A2 (PANSTARRS), C/2021 X1 (Maury-Attard), C/2021 T4 (Lemmon), C/2021 S3 (PANSTARRS), C/2020 V2 (ZTF), C/2020 O2 (Amaral), C/2020 K1 (PANSTARRS), C/2019 T4 (ATLAS), C/2017 K2 (PANSTARRS), P/2014 W1 (PANSTARRS), 364P/PANSTARRS, 347P/PANSTARRS, 326P/Hill, 310P/Hill, 276P/Vorobjov, 242P/Spahr, 237P/LINEAR, 126P/IRAS, 103P/Hartley, 80P/Peters-Hartley, 41P/Tuttle-Giacobini-Kresak, 32P/Comas Sola, 12P/Pons-Brooks, and 2P/Encke. A big thanks to our August contributors: Dan Bartlett, Michel Besson, Michel Deconinck, J. J. Gonzalez, Jose Guilherme de Souza Aguiar, Andrew Hampton, Christian Harder, Scott Harrington, Carl Hergenrother, Eliot Herman, Michael Jäger, John Maikner, Martin Mobberley, Charles Morris, Gary T. Nowak, Mike Olason, Uwe Pilz, Ludovic Prebet, Michael Rosolina, Greg Ruppel, Greg Shanos, Tenho Tuomi, and Chris Wyatt.

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.

This month we welcome two returning periodic comets breaking the 12th magnitude barrier. In April 2024, Halley-type comet 12P/Pons-Brooks will make its first perihelion passage since 1954. On July 20th, it experienced a 4- to 5-magnitude outburst and is now an 11th-magnitude object in the evening sky. Due to peak at 7th magnitude this October, 103P/Hartley is returning for the second time since its superb return in 2010. By the end of this month, 103P should brighten to magnitude 9.5 in the morning sky.

Also visible this month are 8th magnitude C/2021 T4 (Lemmon), 9th magnitude C/2020 V2 (ZTF) and C/2023 E1 (ATLAS), and 11th magnitude C/2017 K2 (PANSTARRS).

Last month the ALPO Comets Section received 180 observations of comets C/2023 E1 (ATLAS), C/2023 A3 (Tsuchishan-ATLAS), C/2022 W3 (Leonard), C/2022 E3 (ATLAS), C/2022 A2 (PANSTARRS), C/2021 T4 (Lemmon), C/2020 V2 (ZTF), C/2020 K1 (PANSTARRS), C/2019 U5 (PANSTARRS), C/2019 T4 (ATLAS), C/2019 L3 (ATLAS), 237P/LINEAR, 126P/IRAS, 103P/Hartley, 80P/Peters-Hartley, 32P/Comas Sola, 12P/Pons-Brooks, and 2P/Encke. A big thanks to our July contributors: Dan Bartlett, J. J. Gonzalez, Jose Guilherme de Souza Aguiar, Christian Harder, Carl Hergenrother, Eliot Herman, John Maikner, Martin Mobberley, Charles Morris, Gary T. Nowak, Uwe Pilz, Michael Rosolina, Greg Shanos, Tenho Tuomi, and Chris Wyatt.

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.

July will be a nice month for comet watchers. While there are no “bright” comets, three comets should make nice targets for binoculars or small telescopes. The brightest comet of the month, 7th magnitude C/2021 T4 (Lemmon), will be well placed for southern hemisphere observers as it races from the morning into the evening sky. Northern observers will be able to observe it early in the month though a bright Moon and a decreasing elevation will make it a bit challenging. Northern observers will have 9th magnitude C/2023 E1 (ATLAS) all to themselves as it moves through the northern circumpolar sky. Both hemispheres can observe 9-10th magnitude C/2020 V2 (ZTF) in the morning sky. Imagers are asked to watch one of next year’s potential bright objects, C/2023 A3 (Tsuchinshan-ATLAS), at 16th magnitude in the evening sky.

Last month the ALPO Comets Section received 99 magnitude estimates, images, and sketches of comets C/2023 E1 (ATLAS), C/2023 A3 (Tsuchishan-ATLAS), C/2022 E3 (ATLAS), C/2022 A2 (PANSTARRS), C/2021 T4 (Lemmon), C/2021 S3 (PANSTARRS), C/2020 V2 (ZTF), C/2020 K1 (PANSTARRS), C/2019 U5 (PANSTARRS), C/2019 T4 (ATLAS), C/2019 L3 (ATLAS), C/2017 K2 (PANSTARRS), 364P/PANSTARRS, 276P/Vorobjov, 237P/LINEAR, 126P/IRAS, 77P/Longmore, 71P/Clark, and 12P/Pons-Brooks. A big thanks to our June contributors: J. J. Gonzalez, Jose Guilherme de Souza Aguiar, Christian Harder, Carl Hergenrother, Eliot Herman, John Maikner, Michael Rosolina, and Chris Wyatt..

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.

May was a quiet month for comet watchers as the sky was lacking in bright or even semi-bright comets. June should bring some improvement. C/2020 V2 (ZTF), which has been around magnitude 9.0 to 9.5 for most of the year, is again visible after passing solar conjunction. C/2021 T4 (Lemmon) and C/2023 E1 (ATLAS) are expected to start the month at 10th magnitude and reach magnitude 9 by the end of the month. C/2021 T4 (Lemmon) is primarily an object for southern hemisphere observers, while C/2023 E1 (ATLAS) is a northern-only object.

Last month the ALPO Comets Section received 60 magnitude estimates and images/sketches of comets C/2023 E1 (ATLAS), C/2023 A3 (Tsuchishan-ATLAS), C/2021 T4 (Lemmon), C/2020 K1 (PANSTARRS), C/2019 U5 (PANSTARRS), C/2019 T4 (ATLAS), C/2019 L3 (ATLAS), C/2017 K2 (PANSTARRS), 364P/PANSTARRS, 263P/Gibbs, 237P/LINEAR, 199P/Shoemaker, 133P/Elst-Pizarro, 130P/McNaught-Hughes, 99P/Kowal, 96P/Machholz, 81P/Wild, 219P/LINEAR, 103P/Hartley, 80P/Peters-Hartley, 77P/Longmore, 71P/Clark, and 12P/Pons-Brooks. A big thanks to our May contributors: J. J. Gonzalez, Jose Guilherme de Souza Aguiar, Carl Hergenrother, John Maikner, and Chris Wyatt.

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.