C/2020 M3 ATLAS

Closest to Sun on 2020 Oct 25 at 1.26AU.

Closest to Earth on 2020 Nov 14 at 0.35AU.

Maximum magnitude 7.5 in Nov 2020.

Orbital period:  138 years

C/2020 M3 ATLAS on 2020 October 18 at 12:20UT.
My visual estimate on Oct 18.74UT was magnitude 7.8 using 15x70mm binoculars.
The comet sported a big coma, 15' across, but quite diffuse. Dark skies were required to see it.

This comet was discovered by the ATLAS survey on June 27th, at magnitude 18.

During August, a report from a Japanese observer indicated that the comet appeared 4 magnitudes brighter than prediction.

I followed up with a visual observation of 11.4 on August 28, 5 magnitude brighter than prediction!

The above image indicates a big coma of 10’. corresponding to an actual diameter of 340,000kms.

This “Halley type” comet has potential to become binocular observable in October-November when well situated in evening skies at opposition.


September 2020
Comet brightened from magnitude 10.5 to 9.0 during the month.

There were several great deep sky rendezvous events this month with galaxies in Fornax and Eridanus.

On September 8, it was 1 degree north of magnitude 9.4 galaxy NGC1316

On September 9, it was 20' north of magnitude 11.5 galaxy NGC1326

On September 12, it was 16' north of magnitude 10.3 galaxy NGC1365

On September 14, it was 16' south of magnitude 10.4 galaxy NGC1399 in the Fornax Galaxy Cluster

On September 27, it was 24' south of magnitude 10.6 galaxy NGC1532


October 2020

On October 1, the magnitude 9.0 comet was in Eridanus, a couple of degrees north of 43 Eri, and well situated for southerners.

Although the comet rose in the east during evening hours, it appeared highest in the morning sky before dawn.

On October 6, it was situated between Ups 1 and Ups 2 Eri.

On October 20, it was a degree west of Epsilon Lepii.

On October 27, it was adjacent to Mu Lepii. At this time the comet had brightened to magnitude 8.0

November 2020
At the start of November, the magnitude 8.0 comet was situated in Lepus, about 3 degrees south of Rigel, trekking slowly northwards.
It rose after sunset, but was best observed during late evening to morning hours.
Around November 6-7, it was 3 degrees west of the Orion Nebula M42
and was a great photographic opportunity to capture both, using a wide field lens, as seen below.

On November 15, it was within a degree of Bellatrix in Orion.

Image of the comet on 2020 November 16, when near reclection nebula VDB38 in Orion.
The comet was closest to Earth at this point and sported a coma size between 15’ to 20’ across.
The comet entered Taurus on November 23 but moonlight started to interfere with evening viewing.
On November 28, it was 2 degrees west of the Crab Nebula M1.

December 2020
On the evenings of December 3-4, the comet was within 1 degree of Beta Taurii, low in the north eastern sky and had faded to magnitude 8.5.
The comet continued its northerly trek through Auriga, best observed around local midnight.
On December 9, it was adjacent to star cluster NGC1893 and IC405 the “flaming star” nebula.

On December 12, it was 2 degrees west of star cluster M38
On December 17, it was 30’ west of star cluster NGC1857. The comet had then faded to magnitude 9.5.