Amazon.com : Telescopes for Adults, 70mm Aperture and 700mm Focal Length Professional Astronomy Refractor Telescope for Kids and Beginners - with EQ Mount, 2 Plossl Eyepieces and Smartphone Adapter : Electronics
Simple Formulas for the Telescope Owner - Sky & Telescope - Sky & Telescope
Astrophotography, Pixel by Pixel: Part 2 - Focal Ratio Effects – Cloud Break Optics
Lecture 7: Optics and Telescopes
Basics Part 1: Understanding Aperture, Focal Length and Focal Ratios – Blackwater Skies
Optical Telescopes | Let's Talk Science
What determines a telescope's fstop? I often see the same size lens with different fstops. - Quora
Everything You Need to Know Before Buying a Telescope | B&H eXplora
Telescope Aperture Explained - YouTube
astronomical optics, part 2: telescope & eyepiece combined
Aperture, focal length and focal ratio - Optics Trade Blog
Optical system of a telescope
How to Choose Eyepieces for Your Astronomy Telescope
f-number - Wikipedia
Formula to estimate exposure from aperture & F ratio - Beginning Deep Sky Imaging - Cloudy Nights
Astro Tutorial #1.5: Focal Length and Aperture - YouTube
focal length - Society for Popular Astronomy
Telescope Focal Length: Everything You Need To Know
focal ratio - Society for Popular Astronomy
Telescope stats explained - BBC Sky at Night Magazine
Tele Vue Optics: How Cameras, Binoculars and Telescopes Work
ZipDob - the Zip Dobsonian - Mel Bartels
