The brightest comet of the year C/2025 F6 Lemmon: when and where to watch in Russia

In the coming days, one of the most spectacular astronomical events of 2025 will be observed over the territory of Russia — the passage of comet C/2025 F6 Lemmon, already named by experts as the brightest comet of the year. In mid-October, it will approach the Earth at a minimum distance. Where to observe a celestial object is in the Izvestia article.

What is known about comet C/2025 F6 Lemmon

Comet C/2025 A6 (Lemmon) was discovered in early 2025 as part of the Mount Lemmon Survey and has been attracting increased attention from the astronomical community ever since. In a few months, the object has significantly exceeded initial expectations in terms of brightness and activity.

According to calculations by the orbital services, the closest passage to Earth is expected on October 21, 2025, at a distance of about 0.596 astronomical units (89 million km), and the passage of perihelion (the minimum distance to the Sun) falls at the beginning of November 2025.

After interacting with the gravity of the Sun, the period of the comet's rotation is estimated at 1150-1350 years, that is, the appearance of this object can be considered a one-time occurrence in modern human history.

In recent months, the comet has shown an increase in brightness: amateur images and professional observations show that it shows signs of tail activity, both dust and ion tail.

Fragments and nodes in the ion tail were recorded in individual frames, indicating interaction with the solar wind and increased core activity. According to recent estimates, the comet is within sight of binoculars and, under favorable conditions, can be discerned with the naked eye from a dark sky. The approximate integral brightness varies around 3.5-5 magnitude during the peak period, but forecasts remain dependent on the behavior of the core in the coming days.

The special feature of C/2025 A6 Lemmon is its greenish hue in the visible light spectrum, which is produced by diatomic molecules emitted when ice is heated near the Sun. It is this coloration that makes the object visible and photogenic to amateur astronomers and astrophotographers.

When and where is the best place to watch comet in Russia

The peak visibility phase for observers in the Northern Hemisphere is from the middle to the end of October 2025, with the best observation opportunity in the days closer to October 21.

At this time, the comet is visible in the evening sky on the west-northwest and northern horizons shortly after sunset. Then, as it moves across the sky, it rises higher and becomes more convenient for observation in large cities and suburban observation platforms.

For residents of the European part of Russia (including Moscow and St. Petersburg), the convenient time for observations is immediately after sunset (in the first 30-90 minutes after dusk), when the sky is still dark enough, but the comet has already separated from the glare of the sun.

Dangerous supermoon in October: how the Harvest Moon will transform everyone's life

The power of the supermoon in Aries will sharpen your senses and help you let go of the past.

In more northern latitudes, the object is almost circumpolar in October and may remain visible longer at night. In the southern regions of Russia, it is better to observe the comet in the early hours of the night, until it descends close to the horizon. For Moscow, the estimated rise/set times and the highest climax can be tracked in online ephemeris calculators.

Methods and conditions of observation: how to choose a place

The key factor is cloud cover and transparency of the atmosphere. Even a bright comet becomes invisible with solid clouds or a high layer of thin clouds (cirri) that scatter light. Therefore, before going out, you should focus on a detailed local forecast: choose windows with clear skies in the first couple of hours after sunset. Weather services and specialized astronomical weather resources are suitable for this.

It is also important to consider light pollution. In urban environments, the brightness of the background significantly degrades the contrast and hides tails and weak comas. Even a small trip outside the city (10-30 km from the metropolis) often solves the problem and increases the chances of noticing the object with the naked eye.