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Optical system of a telescope
astronomical optics, part 2: telescope & eyepiece combined
Seeing and aperture
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Extremely large telescope - Wikipedia
What determines a telescope's fstop? I often see the same size lens with different fstops. - Quora
Telescope Aperture Explained: Does Size Really Matter?
Amazon.com : Meade Instruments – Polaris 114mm Aperture, Portable Backyard Reflecting Stargazing Astronomy Telescope for Beginners –Stable German Equatorial (GEM) Manual Mount – View the Moon, Planets & Stars, One Size, Blue : Electronics
Seeing and aperture
Telescope Focal Ratio: Explanation (F Ratio & F-Number) - Telescope Nerd
Everything You Need to Know Before Buying a Telescope | B&H eXplora
Telescope Size / Aperture Guide - How big of a telescope do you need for visual / astrophotography? - YouTube
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TELESCOPE CENTRAL OBSTRUCTION: SIZE CRITERIA
