This is how you can see the October comets: Lemmon and Swan

This October the night sky brings a double reward: Two comets will stand out in the coming weeks. C/2025 A6 (Lemmon) and C/2025 R2 (SWAN) they appear with very attractive visibility prospects, especially around its closest approaches to Earth.

The comets that can be seen without instruments are not common —barely one or two per decade—and their behavior is capricious. That's why it's worth planning, looking for dark skies, and adjusting expectations: actual visibility will depend on brightness, light pollution and meteorology.

Lemmon and SWAN, the protagonists of the month

C/2025 A6 (Lemmon) is growing rapidly and could become the big attraction of the month: Estimates place it close to magnitude +3 Towards the end of October, a level suitable for dark locations and even for the naked eye. At the beginning of the month, it was around magnitude +6.1 (the limit of the human eye).

On the calendar, Lemmon marks two milestones: the closest approach to Earth on October 21 (≈89 million km) and perihelion on November 8 (≈79 million km from the Sun). During the first half of October it is best observed at dawn; from the 16th it will also begin to appear after sunset. section from October 22 to 28 It will be especially favorable due to the low interference from the Moon.

In the sky, Lemmon will show an increasingly evident comma and one elongated tail with a bluish tone (dominated by ionized gas). If the comet releases more dust, That tail could gain shine by better reflecting sunlight. As usual, variations are not ruled out: could surprise on the upside or turn off earlier than expected.

For their part, C/2025 R2 (SWAN) is the other proper name of the monthIt reached its perihelion on September 12 and It will approach Earth around October 20 (≈0,26 AU; 38–39 million km)It is more favorable from the southern hemisphere and, in October, it gains altitude toward the southwest after sunset.

SWAN transits zones near Libra and Scorpio; at the beginning of the month it passed near Beta Librae and its brightness is around the limit of unaided vision. In good conditions, it can be hunted fleetingly with the naked eye, but 10x50 binoculars will make observation much easier.

Recommended dates and times

The most interesting windows are concentrated in the second half of the month. For Lemmon, between October 12 and November 2 The best nights are expected, with peak visibility around the 21st and a very good period from the 22nd to the 28th due to the limited moonlight.

With Lemmon, start by looking 90 minutes before sunrise in the first half of the month and switches to the evening time slot in the second half, shortly after sunset. On October 16, it will pass close to Cor Caroli (Canes Venatici), a useful reference to locate it.

SWAN will have Best afternoons between October 10 and 23, especially around the 20th, low in the southwest shortly after sunset. If the weather is good, both comets could be seen on the night of the 20th: SWAN to the southwest and Lemmon further west-northwest.

In the first week, the presence of a bright Moon (October 6–7) will complicate the catches; in the last decade of the month, the darkness of the sky will help to squeeze the shine out of both tails.

Where to watch from Spain

The darker the environment, the better. Starlight Reserves and High Mountain Skies marcan la diferencia: La Palma (Roque de los Muchachos) and Tenerife (Teide), Montsec (Lleida), Sierra Nevada (Granada), Sierra Morena (Andalusia), Monfragüe (Extremadura), Gredos (Ávila) or the Picos de Europa offer ideal panoramic views.

For SWAN, prioritizes clear horizons to the southwest (Andalusia and the southern coast of the peninsula work very well). For Lemmon in the late afternoon, focus on the west-northwest, and in the early morning, look northeast.. In the first half of October you can also be guided by the Osa Mayor.

Practical observation tips

Choose moonless nights, arrive early and let your eyes adapt in 20–30 minutes in the dark. Avoid direct light from cell phones or headlights and protect yourself from the wind and cold.

With 10x50 binoculars or a small telescope (70-100mm) you will better distinguish the comma and the tail. Use a tripod if you can; a stable support greatly improves the image and reduces eye strain.

Applications such as Stellarium or Star Walk They'll give you the updated position. Check the weather forecast and sky transparency: Calima or high humidity can turn off significantly the brightness.

Visibility by hemispheres

From the northern hemisphere (including Spain), Lemmon has a head start and should be the most grateful in the last ten days of October.In the southern hemisphere, SWAN is the one that is best placed at the beginning of the month; with binoculars it will be easier follow it as it ascends to the southwest.

Those observing from South America will find that Lemmon becomes less favorable in the north, while SWAN could offer some opportunity in dark skies after sunset. In all cases, light pollution will be the critical factor.

If the weather is good and cometary activity is good, October gives us the option of seeing two comets in the same month and on consecutive nights. With a little planning—and the darkest possible sky—the best dates in the second half of the month can leave unforgettable images.