Seeing and aperture
astronomical optics, part 3: the astronomical image
Avoiding diffraction spikes with an aperture mask - Orion: Astrophotography Talk Forum Forum: Digital Photography Review
Stopping down - Wikipedia
Amazon.com : Telescope for Adults, 70mm Aperture 500mm Refractor Telescope for Astronomy Beginners, 20X-150X, Fully Multi Coated Optics, Portable Travel Telescope with Pro Tripod, Phone Adapter & Backpack : Electronics
Early telescopes
AstroGoods Astronomy Products: Home
astronomical optics, part 2: telescope & eyepiece combined
Newtonian Reflecting Telescope Designer
Photography Jargon – NPC Main
stopping down aperture to increase focal ratio - Beginners Forum (No Astrophotography) - Cloudy Nights
The Advantages and Disadvantages of Stopping Down a Lens – Sunex Inc.
The Advantages and Disadvantages of Stopping Down a Lens – Sunex Inc.
F-number - Wikiwand
Fun with a 5" off-axis aperture mask - why bigger isn't always better. : r/ telescopes
Does an off-axis aperture equal an Apo of same size? - Reflectors - Cloudy Nights
Hobby Killers: What Telescopes Not to Buy - Sky & Telescope - Sky & Telescope
Why and how to make a sub-aperture mask for a refractor | 10 Minute Astronomy
Amazon.com : Telescope for Adults, 70mm Aperture 500mm Refractor Telescope for Astronomy Beginners, 20X-150X, Fully Multi Coated Optics, Portable Travel Telescope with Pro Tripod, Phone Adapter & Backpack : Electronics
What determines a telescope's fstop? I often see the same size lens with different fstops. - Quora
Why and how to make a sub-aperture mask for a refractor | 10 Minute Astronomy
Aperture and Field Stops - YouTube
