Overview
- Both long‑period comets passed closest to Earth on Oct. 20–21 and remain observable this week from northern latitudes.
- Comet Lemmon is the brighter target and can be seen from dark sites without optics, showing a green glow from carbon gases released as it warms.
- Comet SWAN is fainter and typically requires binoculars or a small telescope despite having come closer to Earth than Lemmon.
- Best viewing is about 90 minutes after sunset: look northwest near Arcturus and the Big Dipper’s handle for Lemmon, and southwest below Altair for SWAN.
- Visibility will degrade over the next few nights as the Moon brightens, though Lemmon should persist into early November on its approach to perihelion, with live streams available from projects such as the Virtual Telescope Project.