Formula to estimate exposure from aperture & F ratio - Beginning Deep Sky Imaging - Cloudy Nights
Astrophotography, Pixel by Pixel: Part 2 - Focal Ratio Effects – Cloud Break Optics
astronomical optics, part 2: telescope & eyepiece combined
Newtonian Reflecting Telescope Designer
Q on light gathering power and exposure times - Beginning Deep Sky Imaging - Cloudy Nights
Simple Formulas for the Telescope Owner - Sky & Telescope - Sky & Telescope
Aperture, f-ratios, myths, etc. | Ask Craig | Stark Labs
How to Choose Eyepieces for Your Astronomy Telescope
f-ratio myth
f-number - Wikipedia
Astrophotography, Pixel by Pixel: Part 2 - Focal Ratio Effects – Cloud Break Optics
What is Focal Length – Distance Light Travels in Telescopes
Aperture, focal length and focal ratio - Optics Trade Blog
What does focal ratio mean in telescopes? - Quora
Telescope Focal Ratio Explained - YouTube
Telescopes: Focal ratio, plane and telescope types - YouTube
astronomical optics, part 3: the astronomical image
The f/number, or scope focal ratio, is one of the most important characteristics and specifications of a telescope. It… | Astrophotography, Manifestation, Telescope
Lecture 3
Image Resolution: Effect of Focal Ratio - Beginning Deep Sky Imaging - Cloudy Nights
f-number - Wikipedia
focal ratio - Society for Popular Astronomy
Telescope stats explained | BBC Sky at Night Magazine
Focal Reducer Placement
