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Analysis of Comet Apparitions


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Current Fainter Comets of Interest


On Oct. 31, 2010 A. Boattini discovered a 20.0 mag comet with the 1.5m-Mt.Lemmon-reflector near the border of the constellations Cetus/Aries. Comet C/2010 U3 (Boattini) showed a medium condensed 6-7" coma, elongated in p.a. 330°, harboring a 3-4" central condensation. Additional observations showed a 20" coma and a 25" tail in p.a. 330°. At discovery the comet stood in the record solar distance of 18.5 AU! It will not reach perihelion before spring 2019 at a distance of 8 AU. Nevertheless it could become as bright as 15 mag, then moving through far-northern regions (Camelopardalis, Ursa Major, Draco) (IAUC 9182 / 2010-V109). This implies an inherently bright comet which showed a coma diameter of already 250.000 km at discovery!
An analysis of the apparition, based on only two dozen observations, yields the brightness parameters m0=6.7 mag / n=2. Thus the comet peaked at magnitude 15.8 at the time of perihelion. Throughout the apparition the comet showed a constant coma diameter of about 0.4-0.5' (about 150.000 km).

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On images taken on July 19, 2015 the PanSTARRS team discovered a comet in the constellation Capricornus, near the border to Sagittarius. According to the team comet C/2015 O1 (PanSTARRS) displayed a 2.5" tail towards East and a miniscule coma of magnitude 19.5. Additional observers reported a coma of diameter 15x17" and of total magnitude 18.5 and a 4" tail in p.a. 100°. The comet will pass its rather distant perihelion (distance: 3.7 AU) in February 2018, expected to reach magnitude 13.5 (CBET 4119 / MPEC 2015-Q71). It should be brighter than 16 mag between January 2017 and April 2019. During this period it will move from Aquila through Hercules, Bootes, Ursa Major into Lynx. Thus it will be comfortably placed in the morning/night sky for mid-European observers during the interesting weeks.
Based on 126 observations from 24 observers the brightness estimates can be best represented by the parameters m0=4.5 mag / n=4, which imply a maximum brightness of 12.8 mag at the opening of April 2018. Whereas the coma measured only 0.7' (110.000 km) in diameter in spring 2017, the reports indicate the maximum coma diameter of 1.4' (200.000 km) in spring 2018. In winter 2018/19 it still measured 1.2', indicating a diameter of 225.000 km. During the apparition the coma got more and more diffuse. The degree of condensation was DC 4-5 in spring 2017, DC 4 in spring 2018, but only DC 2 in winter 2018/19.

Total Brightness and Coma Diameter

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On July 14, 2016 the PanSTARRS team discovered a comet of magnitude 21 in the constellation Hercules. Follow-up observations of comet C/2016 N6 (PanSTARRS) showed a strongly condensed 5x7" coma of total magnitude 20.0. The comet will pass perihelion at a solar distance of 2.7 AU in July 2018, expected to reach 14 mag (CBET 4309). It should be brighter than 16 mag between fall 2017 and spring 2019, with maximum brightness in spring 2018. During this period it will move through the constallations Bootes, Draco, Ursa Minor, Draco, Lynx (maximum brightness), Cancer, Hydra, Puppis, Canis Major and Lepus. Between mid-June and the start of September 2018 it will not be visible from mid-European sites.
Based on 174 observations from 29 observers the comet showed a very continuous brightness development, which can be well represented by the formula

m = 5.3 mag + 5×log D + 10.5×log r,

indicating a maximum brightness of 12.3 mag, which was reached at the beginning of April 2018 and at the opening of December 2018. The apparent coma diameter measured only 0.5' in 2017, but started to increase in February 2018, reaching 1.5' in May. In fall it reached its maximum of short of 2'. Thereafter it decreased, measuring short of 1' at the start of April 2019. The absolute coma diameter measured only 95.000 km in 2017, but started to increase in February 2018, reaching 225.000 km in May. In fall it peaked at 250.000 km. Thereafter it shrunk, measuring 125.000 km at the start of April 2019. The degree of condensation was constant at DC 3 in 2017, peaking at DC 5 in spring 2018, and was estimated at DC 4 in fall 2018 and DC 2-3 at the start of April 2019. Only CCD-observers detected a tail, with the length never exceeding 3' (1 Mill. km).

Total Brightness and Coma Diameter

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On images taken on Aug. 26, 2016 the PanSTARRS team discovered a comet on the border of the constellations Capricornus/Aquarius, estimating the brightness to be about 21.5 mag, noticing a broad, 6" tail towards North. Detailed observations of comet C/2016 Q2 (PanSTARRS) showed a strongly condensed, 12" coma of total magnitude 19.0 and a very broad 12" tail in p.a. 338°. The comet (with an orbital period of about 440 years) will pass its perihelion at the large distance of 7.2 AU in May 2021, expected to reach about 15.5 mag. It should be brighter than 16 mag between spring 2020 and fall 2022, moving through the constellations Cygnus, Lyra, Draco/Hercules towards Ursa Major during this period (CBET 4311 / MPEC 2016-V116).

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In the course of the LINEAR Sky Survey an asteroidal object of magnitude 19.5 was discovered on images taken on Jan. 26, 2017 near the border of the constellations Hydra/Corvus. Follow-up observations of comet C/2017 B3 (LINEAR) showed a significantly condensed 8" coma of total brightness 18.5 mag. This comet will pass perihelion at the beginning of 2019, expected to peak around magnitude 14-15 (CBET 4354). However, at this time it will be positioned in the far Southern Sky. It will not be observable from mid-European locations during the time interval when it is expected to be brighter than 16.0 mag.
This comet is under surveillance by amateurs since spring 2017. Because it was in conjunction with the Sun at perihelion the maximum brightness was reached during its opposition in summer 2019. The comet showed a quite continuous brightness development which can be well described by the parameters m0=7.0 mag / n=3, which yield a maximum brightness of 14.5 mag. In summer 2019 it showed a moderately condensed 0.7' (100.000 km) coma.

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On May 21, 2017 the PanSTARRS team discovered a comet of magnitude 21.0 with a miniscule coma in the constellation Draco. Follow-up observations of comet C/2017†K2 (PanSTARRS) showed a moderately condensed 12" coma of total magnitude 19.0 (CBET 4393 / MPEC 2017-N26). The comet was detected in the record distance of 16.1 AU, indicating an absolute brightness of 1 mag and an absolute coma diameter of 140.000 km. The comet will reach perihelion at a distance f 1.80 AU not prior to the Christmas days 2022. It should be brighter than 16.0 mag from early 2020 to the end of 2025. During this interval it will move from the northern parts of Hercules through Ophiuchus and Scorpius, diving far south between October 2022 and March 2023, then reappearing for mid-European observers in Eridanus, then moving through Lepus, Orion and Taurus into Auriga. Its maximum brightness of about 5.5 mag should be reached around the turn of the years 2022/23. During the most interesting months it will be observable from mid-European locations in the evening sky until the end of August 2022 (then of magnitude 6.0), then from early September 2023 (then of magnitude 9.5) onwards in the morning sky.

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On June 21, 2017 the ATLAS team discovered an asteroidal object of magnitude 18.0 in the constellation Cepheus, which revealed its cometary nature during follow-up observations. Comet C/2017 M4 (ATLAS) showed a moderately condensed 13" coma of total magnitude 17.5 and a short tail pointing SW. It will reach perihelion at a distance of 3.24 AU not prior to Jan. 15, 2019, expected to reach 14.0 mag in summer 2019 (CBET 4408 / MPEC 2017-N58). It will be brighter than 16.0 mag during the whole year of 2018 thereby moving from the border of the constellations Cygnus/Lyra through Hercules (maximum brightness) into Ophiuchus. From mid-European locations it will be observable until November 2018.
The comet developed very continuously. Based on 63 observations from 16 international observers the brightness developed according to the parameters m0=7.5m / n=2.8, yielding a maximum brightness of 13.2 mag at the opening of May 2019 (a secondary maximum of 14.0 mag was reached at the start of August 2018). The diameter of the moderately condensed (DC 4) coma was about 0.8' (appx. 125.000 km) during summer 2018 and about 1.0' (appx. 140.000 km) in spring 2019. No tail was observed.

Total Brightness and Coma Diameter

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On Jan. 15, 2018 A.R. Gibbs discovered a 19 mag comet in Leo. Follow-up observations of comet C/2018 A6 (Gibbs) showed a highly condensed, 10" coma of total magnitude 18.8 and a fan-shaped 15" tail (PW=110-17°). The comet will pass perihelion in the solar distance of 2.86 AU on May 24, 2019, expected to peak at magnitude 15 (CBET 4479). However, after the start of 2019 (then 16.0 mag) it will be situated far in the southern sky.
The development of this comet can only be described roughly, since only 25 observations from international observers have been published. The brightness development can be best described by the parameters m0=4.5 mag / n=6, resulting in a maximum brightness of 14.0 mag in early summer. Observers reported a coma diameter of about 0.7' (appx. 90.000 km), with a degree of condensation of DC 5.

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In the course of the ATLAS project a comet was discovered on June 6, 2018 in Centaurus. Comet C/2018 L2 (ATLAS) showed a 20" coma of total magnitude 15.5 and a 27" tail in p.a. 92°. It will pass perihelion on Dec. 2, 2018 at the solar distance of 1.71 AU, when it is expected to reach magnitude 14.0 (CBET 4522). It should be brighter than 16 mag until April 2019. The comet will be visible from mid-European locations between October 2018 and April 2019 low above the evening horizon (SW to NW at altitudes of less than 20°) and in the morning sky during the first four months of 2019 above the eastern horizon (maximum altitude: 25°). During this interval it will move through Serpens, Ophiuchus, Hercules, Vulpecula, Cygnus and Lacerta into Andromeda.
According to 42 observations from 22 international observers the comet showed an outburst with a magnitude of more than 3.5 mag! Whereas the comet was of total brightness 13.8 mag on Sep. 5, 2018, the observers reported a magnitude of 10.1 on Oct. 1, 2018. After Oct. 6 (60 days prior to perihelion) the comet faded slowly, according to the formula

t > -60d: m = 9.0 mag + 5×log D + 0.015×(t-T),

but was still of magnitude 12.0 at the opening of March 2019 and of magnitude 13.0 at the end of this month. The coma diameter developed in a manner typical of an outburst. Whereas it measured 1.0' (100.000 km) at the start of September 2018, it swallowed to 4.0' (430.000 km) shortly after the outburst. Thereafter it decreased, measuring 2.0' (200.000 km) at the opening of February 2019 and 0.7' (85.000 km) at the end of March. Surprisingly, the outburst had no impact on the development of the degree of condensation. Until end of 2018 it was constant at DC 3-4. In 2019 the coma got more and more diffuse, reaching DC 2 at the opening of March. A tail was not observed.

Total Brightness and Coma Diameter

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On July 7, 2018 the ASASSN team discovered a comet of magnitude 16 in the central part of Eridanus. Follow-up observations of comet C/2018 N2 (ASASSN) showed a strongly condensed 25" coma and a 15" tail in p.a. 220°. The comet will pass perihelion on Nov. 11, 2019 at a distance of 3.13 AU, expected to reach magnitude 11 (CBET 4534). It should be brighter than 16 mag until spring 2021, brighter than 13.5 mag between mid-2019 and mid-2020. During the latter time span it moves from Aries into Cepheus. Thus it will be well placed for mid-European observers during the most interesting weeks. Assuming an average activity parameter (n=4) the absolute brightness is magnitude 4.0, hinting towards a large object, which, alas, will not come close to the Sun.
At the opening of August 2019 48 observations from 10 observers can be used for a first preliminary analysis. So far the brightness evolves according to the parameters m0=7.5 mag / n=2, indicating a development clearly below average. If this development should continue the comet will peak at only 11.5 mag at perihelion. At the end of 2018 the 14.0 mag comet showed a coma of diameter 0.8' (170.000 km) and a degree of condensation of DC 3-4. In July 2019 the comet was of magnitude 12.5, showing a significantly condensed (DC 5) coma of diameter 1.0' (150.000 km). No tail has been reported so far.

Total Brightness and Coma Diameter

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An asteroidal object of magnitude 20, discovered by the Lemmon project already on Oct. 27, 2018 near the borders of the constellations Cygnus/Lyra/Draco, showed its cometary nature by follow-up observations. Comet C/2018 U1 (Lemmon) showed a stellar coma and a 5" tail pointing eastward. It will pass perihelion in the solar distance of 4.98 AU on Nov. 1, 2021, expected to reach 15.0 mag (CBET 4574). Between spring 2021 and summer 2022 it should be brighter than 16.0 mag. However, for mid-European locations it will disappear already in September 2021. During this interval it will move from the eastern part of Serpens through Ophiuchus to the northern part of Scorpius.

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Comet C/2018 W1 (CATALINA), which was discovered by the CATALINA team on Nov. 16, 2018 in the eastern part of Andromeda and passed its perihelion on May 11, 2019 at a solar distance of 1.36 AU, surprised the observers in the southern hemisphere in a very positive way. Based on the discovery magnitude of 19.0 and assuming a standard development (n=4) a maximum brightness of 16.0 mag was predicted. However, the comet reached a maximum brightness of 11.5 mag in May 2019! The brightness parameters, derived from only a small number of observations, are m0=7.5 mag / n=8, indicating that the comet had been brighter than 16.0 mag between January and August 2019. In May 2019 it showed a moderately condensed (DC 3) coma of diameter 2.5' (190.000 km).

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On Feb. 26, 2019 Heather Flewelling discovered a comet in the constellation Scutum in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS). Comet C/2019 D1 (Flewelling) was of magnitude 15.5, showing a highly condensed, 20" coma and a 1.5' tail in p.a. 260°. It will pass perihelion in the solar distance of 1.58 AU on May 11, 2019, expected to reach magnitude 14 (CBET 4614). It should have faded to magnitude 16 at the end of September. During this period it should move through the constellations Aquila, Delphinus, Pegasus, eventually reaching Andromeda. Thus it will be an object in the morning sky.
A scant 25 observations allow only a rough analysis. According to these the brightness developed according to the parameters m0≈5.0 mag / n≈15, indicating a surprisingly rapid development. The maximum brightness of 13.5 mag was reached in May 2019 with the comet showing a well-condensed (DC 5) coma of about 0.7' (appx. 45.000 km) diameter.

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On March 29, 2019 B.M. Africano discovered a comet near the border of the constellations Bootes/Libra on images taken in the course of the Mount Lemmon Survey. G.V. Williams recognized that this object had already be announced the night before by the "Asteroid Terrestrial Impact Last Alert System" (ATLAS). Comet C/2019 F1 (ATLAS-Africano) showed a highly condensed coma of diameter 10" and total magnitude 18.5 and a hint of a tail towards NW. The comet will pass perihelion in the solar distance of 3.60 AU on June 23, 2021, expected to peak at magnitude 13.5 (CBET 4619). However, at this time it will be positioned near the celestial South Pole. It should be brighter than 16 mag between spring 2020 and late summer 2022. During this period it will move from the southwestern part of Libra through the constellations Hydra and Lupus towards Octans. Thereafter it will slowly move northward, reaching Fornax in late summer 2022. Mid-European locations will lose sight of the comet in June 2020, when the comet is expected to be of magnitude 15.5.

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Quan-zhi Ye of the California Institute of Technology discovered a comet near the border of the constellations Andromeda/Cassiopeia on images taken with the 1.2m-Schmidt-telescope on Mt. Palomar Observatory on May 9, 2019. Comet C/2019 J2 (Palomar) showed a considerably condensed 8" coma of total magnitude 17.0 and a faint 20" tail pointing towards SW. The comet will reach perihelion on its 316 years orbit on July 19, 2019 at the solar distance of 1.73 AU, expected to reach 15.5 mag (CBET 4626/ MPEC 2019-O96).
Actually the comet peaked at magnitude 15.0 in mid-June 2019, showing a 1' coma. However, only a very small number of observations have been published. Then, at the opening of July, it began to disintegrate (The Astronomerís Telegram No. 12931).

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On images taken on May 16, 2019 in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) a comet was discovered in the southern part of Ophiuchus. Comet C/2019 K1 (ATLAS) showed a 5" coma of total magnitude 17.5 and a fan-like tail of 10" length, pointing towards West. It will pass perihelion on Feb. 12, 2020 at the solar distance of 2.01 AU, expected to reach 14.5 mag (CBET 4629/43). It should be brighter than 16 mag between October 2019 and May 2020. At this time however, it will start moving from Lupus into the far-southern sky (reaching Pavo and Tucan), only to move northwards thereafter (towards Eridanus). Thus it will not at all be observable from mid-European locations.

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On images, taken in the course of the ATLAS project on May 30, 2019 Ken W. Smith discovered a comet of magnitude 18 near the border of the constellations Piscis Austrinus / Grus. Follow-up observations of comet C/2019 K7 (Smith) showed a strongly condensed 12" coma of total magnitude 17.0 and a 90" tail at p.a. 340°. The comet will pass perihelion at the solar distance of 4.48 AU on June 16, 2020, expected to reach magnitude 15.5 (CBET 4645/48). At this time it will move through the constellations Delphinus and Sagitta, thus be observable the whole night.

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On June 10, 2019 the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS)-Team discovered an asteroidal object of magnitude 19 near the border of the constellations Lacerta/Andromeda. Follow-up observations showed a strongly condensed 8" coma of magnitude 18.5, but no tail. Comet C/2019 L3 (ATLAS) will pass perihelion at the solar distance of 3.57 AU not before Jan. 10, 2022 (CBET 4644). Assuming an activity factor of n=4 it will peak at magnitude 12, assuming n=3 at magnitude 13. It should be brighter than 16 mag between fall 2020 and spring 2023. During this interval it will move through the constellations Cassiopeia, Perseus, Auriga, Gemini (perihelion), Canis Minor, Hydra, Antlia and Pyxis and should be observable from mid-European locations until the end of 2022.

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On images taken in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) on July 5, 2019, an asteroidal object of magnitude 19 was discovered in Cepheus. Follow-up observations showed a strongly condensed 12" coma of total magnitude 18.0 mag and an 8" tail in p.a. 135°. Comet C/2019 N1 (ATLAS) will pass perihelion at the solar distance of 1.70 AU on Dec. 2, 2020 (CBET 4650). Assuming an activity parameter of n=4 the comet will peak at magnitude 10.5, assuming n=3 at magnitude 12.0. It should be brighter than 16 mag between the beginning of 2020 and fall 2021. For mid-European locations it will disappear above the evening horizon in mid-September 2020, when it should have brightened to 13.0 mag or 12.0 mag. During this interval it will move through the constellations Draco, Ursa Major, Canes Venatici and Coma Berenices. Thereafter it will move towards the Southern Sky.

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Comet 60P/Tsuchinshan (P=6.58a) will pass perihelion for another time on Dec. 11, 2018 in the solar distance of 1.62 AU. In November 2018 it should become brighter than 16 mag, brightening to 14.5 mag until mid-February 2019. The comet moves from the southwestern part of Leo towards the border of the constellations Virgo/Sextans, being visible in the morning sky.
For the final analysis 70 observations from 21 international observers could be used. These yield a brightness development according to the formula

m = 12.5m + 5×log D + 5×log r

Considering that this comet is an old periodic one the derived activity parameter is unusually small. The comet peaked at 13.3 mag in mid-February 2019. Due to the approach to Earth until the end of February the apparent brightness increased more slowly during the first weeks, fading significantly more rapid thereafter. The apparent coma diameter increased continuously from 0.4' at the start of the apparition to the maximum of 1.1' at the end of February 2019. Thereafter it decreased, reaching 0.6' at the end of May. Contrary, the absolute coma diameter remained rather constant between 40.000 and 45.000 km. The degree of condensation was DC 4 at the start of the apparition, increasing to DC 5 until the opening of February 2019. Thereafter it decreased, reaching DC 2-3 at the start of April. A tail, pointing constantly towards NW, was observed between mid-November 2018 and end of February 2019, reaching up to 5' (500.000 km).

Total Brightness and Coma Diameter

FGK observations

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On Nov. 9, 2019 comet 68P/Klemola (P=11.0a) will pass perihelion at the distance of 1.79 AU for an additional time. It should be brighter than 16 mag between May 2019 and February 2020. During this interval it will move along the ecliptic from Ophiuchus towards the border of the constellations Aquarius/Pisces. For mid-European locations it will thus be observable above the evening horizon at rather low altitudes.
Since May 2019 the comet is observed by amateurs. At magnitude 16 at first it reached magnitude 14.0 at the start of August. Based on 30 observations the brightness parameters m0=7.3 mag / n=8 are derived, pointing towards a maximum brightness of 13.5 mag in mid-October. At the start of August the rather diffuse (DC 3) coma was of diameter about 1'.

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Comet 78P/Gehrels (P=7.23a) can be observed during winter 2018/19, reaching perihelion on Apr. 2, 2019 at the solar distance of 2.01 AU. However, at this time it will be situated too near the Sun for observations. For mid-European observers it will be situated low above the evening horizon, moving from the northeastern part of Capricornus towards the border of the constellations Pisces/Cetus. It should brighten from magnitude 13.5 to 13.0.
Until the start of February 2019 only 27 observations from 8 observers came to my knowledge. The brightness estimates can be rather well represented by the parameters m0=9.5 mag / n=3, indicating a maximum brightness of 13.5 mag at the start of October 2018. At the same time the diameter of the medium-condensed (DC 3-4) coma reached its maximum of 1.0' (75.000 km). No tail was reported.

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In autumn 2018 comet 123P/West-Hartley (P=7.58a) should become brighter than 16.0 mag. It will pass perihelion at the distance of 2.13 AU on Feb. 5, 2019, expected to reach magnitude 13. In winter 2018/19 it will make an opposition loop near the borders of the constellations Leo Minor/Leo/Ursa Major.
The development of the comet during this apparition has been analysed using 98 observations from 15 international observers. The brightness estimates can be well represented by the parameters m0=8.8 mag / n=4.5, yielding a maximum brightness of 12.9 mag at the end of February 2019. The apparent coma diameter increased from 0.8' at the start of the apparition to the maximum of 2.0' in mid-March. Thereafter it decreased, reaching 1.3' at the end of May. The absolute coma diameter increased from 55.000 km at the start of the apparition to the maximum of 110.000 km at the end of February. This value was then hold until the end of the apparition. Surprisingly, the coma grew ever more diffuse throughout the apparition; the degree of condensation decreased from DC 5-6 to DC 2. Very few observers reported a tail up to 2' (700.000 km) in February.

Total Brightness and Coma Diameter

FGK observations

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At the beginning of July 2019 comet 260P/McNaught (P=6.89a) should become visible as an object of about magnitude 15.0 in the morning sky. Until mid-August it is expected to brighten to 13.0 mag. During this period it will move from the southwestern part of Cetus into Aries. It will pass perihelion in the solar distance of 1.42 AU on Sep. 9, 2019, expected to reach 12.0 mag.
Until the beginning of August 2019 only a small number of observations have been published. According to these the comet was of magnitude 14.0 at the end of July, showing a moderately (DC 5) condensed coma with a diameter short of 1'.

Andreas Kammerer


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