C/2019 Y4 (ATLAS)

We adopt the upper envelope of the domain defined by visual observations as the visual light curve of the comet. Ferrin (2005) y Sosa – Fernández (2009). New visual observations !!! continues on course at magnitude 0 or a disintegration.

C/2019 Y4 (ATLAS) = C/1844 Y 1. Possibly fragment of Great Comet nucleus
Reported observations:
2020 Mar. 28.97 UT: m1=7.9, Dia.=7', DC=5, ... 7x50 B ... Toni Scarmato (Calabria, Italia)
2020 Mar. 24.78 UT: m1=8.2, Dia.=11', DC=5, ... 25.4-cm L(48x) ... Alexsandr Morozov (Novozybkov, Russia) [method M, Lm=6.72]
2020 Mar. 21.43 UT: m1=8.9, Dia.=6.5', DC=2/, ... 40.0-cm L f/4.5(36x) ... Seiichi Yoshida (Ibaraki, Japan)
2020 Mar. 19.21 UT: m1=8.0, Dia.=15', DC=1/, ... 20x80 B ... Charles Morris (Dream Weaver Observatory, Fillmore, California, USA)
2020 Mar. 18.80 UT: m1=8.0, Dia.=12.5', DC=3, ... 12.0-cm R f/5(30x) ... Maik Meyer (Linter Germany)
2020 Mar. 15.77 UT: m1=8.5, Dia.=10', DC=4/, ... 25.4-cm L(30x) ... Alexsandr Morozov (Novozybkov, Russia) [method M, Lm=6.35]
2020 Mar. 14.91 UT: m1=8.8, Dia.=13', DC=4, ... 15-cm L(30x) ... Carlos Labordena (Castellón, España)
2020 Mar. 14.90 UT: m1=8.6, Dia.=12', DC=3, ... 8-cm B(11x) ... Carlos Labordena (Castellón, España)
2020 Mar. 14.85 UT: m1=8.2, Dia.=12', DC=3, ... 10x50 B ... Juan Jose Gonzalez (Alto del Castro, Leon, Spain, 42º 55' N, 5º 48' W, alt. 1720 m) [Sidgwick method. Tycho-2 comparison stars. SQM: 21.4]
2020 Mar. 13.73 UT: m1=9.5, Dia.=6.5', DC=4, ... 25.4-cm L F/4.7(70.5x) ... Danil Sidorko (Korenovsk, Russia)
2020 Mar. 12.91 UT: m1=9.3, Dia.=7', DC=4, ... 30-cm L(69x) ... HAR11
2020 Mar. 12.81 UT: m1=8.9, Dia.=&7', DC=2, ... 20-cm L(42x) ... SCH04
2020 Mar. 12.80 UT: m1=9.0, Dia.=7', DC=2, ... 12-cm R(30x) ... Maik Meyer (Germany)
2020 Mar. 12.77 UT: m1=9.6, Dia.=7', DC=3, ... 10-cm B(25x) ... GUZ
2020 Mar. 12.73 UT: m1=10.2, Dia.=2.5', DC=5, ... 25.4-cm L F/4.7(70.5x) ... Danil Sidorko (Korenovsk, Russia)
2020 Mar. 06.45 UT: m1=11.5, Dia.=5', DC=4, ... 38-cm L(64x, 142x) ... Bob King (Duluth, Minnesota, USA) [Diffuse coma but significantly larger and brighter than when last observed on Feb. 20 UT. Visible at low magnification. No enhancement with a Swan filter]
2020 Mar. 05.27 UT: m1=10.7 CCD G, Dia.=12.4', DC=-, ... 28-cm T f/2.2 + CCD G ... Terry Lovejoy (remote H06, Mayhill, Australia)
2020 Mar. 03.88 UT: m1=12.4 CCD G, Dia.=2.4', DC=-, ... 28-cm T f/2.2 + CCD G ... Michael Jäger (Austria)
2020 Mar. 02.77 UT: m1=12.2 CCD, Dia.=4', DC=-, ... 25.0-cm T + CCD ... Johan Warell (Sweden)
2020 Feb. 29.96 UT: m1=11.9, Dia.=1.5', DC=3, ... 25.4-cm L(120x) ... Alexsandr Morozov (Novozybkov, Russia)
2020 Feb. 28.77 UT: m1=12.2 CCD, Dia.=5.3', DC=-, ... 25.0-cm T + CCD ... Johan Warell (Sweden)
2020 Feb. 28.15 UT: m1=11.5 CCD G, Dia.=0.25', DC=-, ... 28-cm T f/2.2 + CCD G ... Michael Jäger (Austria)
2020 Feb. 24.22 UT: m1=13.3, Dia.=0.9’, DC=3/, ... 41-cm L(70x) ... Alan Hale (Cloudcroft, New Mexico, USA)
2020 Feb. 20.10 UT: m1=13.8, Dia.=1.3', DC=4, ... 38-cm L(242x) ... Bob King (Duluth, Minnesota, USA)
2020 Feb. 19.94 UT: m1=11.7, Dia.=3', DC=2, ... 20-cm SCT(77x) ... Juan Jose Gonzalez (Alto del Trichero, León, Spain)
2020 Feb. 19.86 UT: m1=13.3 CCD, Dia.=4.7', DC=-, ... 25.0-cm T + CCD ... Johan Warell (Sweden)
2020 Feb. 18.93 UT: m1=14.4, Dia.=0.7', DC=3, ... 60.0-cm L f/4 (305x) ... Sandor Szabo (Sopron, Hungary)
2020 Feb. 18.81 UT: m1=14.7, Dia.=0.5', DC=4, ... 60.0-cm L f/4(305x) ... Sandor Szabo (Sopron, Hungary) 
2020 Feb. 18.39 UT: m1=12.5 CCD, Dia.=4', ... 28-cm SCT + CCD ... Michael Mattiazzo (T68 New Mexico remotely, Australia)
2020 Feb. 17.28 UT: m1=12.2 CCD, Dia.=8.6', ...  50-cm f/6.8 L + CCD + f/4.5 focal reducer ... Thomas Lehmann (T11 New Mexico remotely, Weimar, Germany)
2020 Feb. 17.10 UT: m1=14.0, Dia.=0.5', ... 38-cm L ... Bob King (Minnesota, USA)
2020 Jan. 06.18 UT: m1=17.8, ... H21