S&T Readers: Join the AAS as an Amateur Affi liate Member! We invite you to join the American Astronomical Society, the major international organization of professional astronomers. Benefi ts: * Subscribe to Sky & Telescope at the discounted AAS affi liate rate * Register at reduced rates for AAS and Division meetings * Receive discounts on AAS-IOP books, Annual Review journals, and more * Stay current with the members-only AAS News Digest and email alerts * Access the AAS online store, car rental & hotel discounts, etc. Interested? Please go to: aas.org/join Image: NGC 6891, a bright, asymmetrical planetary nebula in the constellation Delphinus, the Dolphin. (NASA) sk yand tele scope .o r g * MARCH 2025 59http://www.airy-disk.com http://diffractionlimited.com http://www.aas.org/join http://skyandtelescope.org