Hi all,
I'm starting to explore visual astronomy and due to a lack of experience I'm wondering whether in visual astronomy slower focal ratios mean dimmer images, given the same aperture and the same magnification (and the same skies).
For example a 10" f/4 and a 10" f/15 at the same location, as long as eyepieces are matched so magnification remains the same in both telescopes, my gut feeling tells me that image brightness should remain the same