Overview

• Both comets are currently near magnitude 5.8–6, making them binocular targets now with brief daily windows: SWAN about 90 minutes after sunset low in the southwest and Lemmon about 90 minutes before sunrise in the northeast.
• Closest approaches are forecast next week, with SWAN passing about 24 million miles from Earth on October 20 and Lemmon about 55 million miles on October 21.
• Lemmon and SWAN are long‑period comets; SWAN’s orbit is about 22,554 years, and modeling indicates Jupiter shortened Lemmon’s period by roughly 200 years during an April 2025 encounter.
• Discovery credits go to Mount Lemmon Observatory’s Catalina Sky Survey for Lemmon and to Ukrainian amateur Vladimir Bezugly using SOHO’s SWAN instrument for SWAN.
• Astronomers caution that comet brightness can change quickly, so observers should use apps or charts to track positions and consider the Virtual Telescope Project’s planned livestream if local skies are poor.