Comet Lemmon in the sky above Iceland

Comet C/2025 A6 (Lemmon) can be found in the sky above Iceland in October and November. It is barely visible to the unaided eye at a dark location but is an easy target with binoculars or telescopes and a joy to Icelandic astrophotographers.

Comet Lemmon is a wonderful object to photograph. Gísli Már Árnason, Iceland at Night photographer, took these beautiful images of the comet on Saturday night, October 18 2025. An auroral substorm occurred at the same time, illuminating heaven and Earth.

How can I see comet Lemmon?

In October, comet Lemmon is best seen low in the evening sky in the west. The simplest way to catch it is to:

1. Look towards West around 8 PM
2. Use smartphone apps such as Stellarium or theskylive.com to see its location
3. Scan the area using binoculars
4. Be patient while searching for it 

Through binoculars, the comet looks like a small fuzzball. The tail is not very obvious but still visible. It's coma looks pale greenish. The green color can be traced to diatomic carbon (C2) that breaks down in the sunlight and emits green light when excited.

The green color is easily seen in the image below taken by Gísli Már Árnason using Nikon Z8 camera on a 160mm refractor in the Hótel Rangá Observatory on Tuesday, October 21.

When is Comet Lemmon closest to Earth?

Comet Lemmon was closet to Earth on Tuesday October 21 2025, than at 89.2 million kilometers away from us or just over half the average distance between the Earth and the Sun. At that time, the comet flew past Earth at a speed of 217.000 kilometers per hour.

Here you can see where Lemmon is in our solar system.

After October 21, the comet lowers in the sky as seen from Iceland. Between October 21 and 24, it is in the constellation of Boötes the Herdsman and moves into the Serpent and Ophiuchus in November. Then it is better to see it from 7 PM.

Why is it called Comet Lemmon?

The comet was discovered in a survey program called Mount Lemmon Survey and is named after that. It was discovered on images taken on January 3rd, 2025 and is the sixth comet to be discovered that year. That's why it received the catalog number 2025 A6.

The comet's orbit around the Sun pre perihelion was 1350 years. After perihelion on November 8, the orbital period decreases down to 1150 years. Lemmon will therefore return in Earth's sky around the year 3175.