Overview
- Both long‑period comets reached closest approach around Oct. 20 (SWAN about 24 million miles; Lemmon about 55–56 million miles) and are expected to remain near their brightest Oct. 21–22.
- The prime viewing window is roughly 90 minutes after sunset, with Lemmon low in the northwest near Arcturus and Izar and SWAN low in the southwest below Altair in Aquila.
- Binoculars and dark‑sky conditions are recommended, with reported brightness around magnitude +4.9 for Lemmon and +5.8 for SWAN, and optical aid needed to see tails.
- Lemmon also offers a short predawn opportunity on Oct. 21 before it transitions to evening‑only viewing, and growing moonlight later this week will make both comets harder to see.
- The Virtual Telescope Project is livestreaming the comets for viewers unable to observe them directly due to weather or light pollution.