Final Opportunity to Observe Comets Lemmon and SWAN Before Moonlight Obscures View

Skywatchers have a final opportunity to observe Comets Lemmon (C/2025 A6) and SWAN (C/2025 R2) on Saturday, October 25, before increasing moonlight diminishes their visibility. Comet Lemmon will be positioned in the northwest sky, near the constellation Serpens, while Comet SWAN will appear in the south, below the Summer Triangle stars and near Saturn. The optimal viewing window is approximately 90 minutes after sunset, with both comets visible in opposite parts of the sky. For example, in New York City, where sunset occurs at 5:57 p.m. EDT, the ideal time for observation is between 7:27 and 7:57 p.m. EDT. A 16% illuminated waxing crescent moon will be low in the southwest, providing dark conditions before it brightens later in the week. To locate Comet Lemmon, observers should look above the bright star Arcturus, low on the northwest horizon. Tracing the stars in the Big Dipper's curved handle leads to Arcturus; from there, moving at a right angle leads to Rasalhague, the brightest star in the constellation Ophiuchus. In New York, the comet will appear about 20 degrees above the northwest horizon at 7:27 p.m. EDT, gradually sinking as twilight deepens. Comet SWAN will be visible in binoculars, low in the south-southwest after sunset, in the constellation Aquarius, above the 'Teapot' asterism of Sagittarius, and below and to the left of bright Altair in the Summer Triangle. For mid-northern observers, another method is to look halfway between Altair and the bright star Fomalhaut. In New York, SWAN will be about 43 degrees high at 7:27 p.m. EDT before slowly descending toward the horizon. Both comets are expected to remain visible with binoculars through the end of October.