Come join the friendliest, most engaging and inclusive astronomy forum geared for beginners and advanced telescope users, astrophotography devotees, plus check out our "Astro" goods vendors.
Come join the friendliest, most engaging and inclusive astronomy forum geared for beginners and advanced telescope users, astrophotography devotees, plus check out our "Astro" goods vendors.
I believe it has to do with F-ratio and size of the central obstruction. The larger central obstruction the more light is distributed from the airy disk to the first diffraction ring. Faster newts tend to have lager secondary mirrors compared to slower.