While FOV tells you how much sky you see, Pixel Scale tells you how fine the detail is within that sky. It is calculated with a different constant.
The core mechanics of these calculators rely on a standard optical formula:
Here is some text that could be used for an "astro FOV calculator 2021": astro fov calculator 2021
Pinpoint. Sharp. The Orion Nebula was a distinct, glowing patch of color. The rocks in the foreground were sharp.
To give you an idea of how focal lengths interact with sensor sizes (assuming a standard APS-C or Full-Frame sensor), consider these common equipment brackets: Focal Length Range Setup Type Ideal Targets Wide-angle camera lens Milky Way core, constellations, meteor showers 135mm – 300mm Telephoto lens / Small Refractor Andromeda Galaxy (M31), North American Nebula, Rho Ophiuchi 400mm – 700mm Medium Refractor / DualtED Orion Nebula (M42), Rosette Nebula, Pleiades (M45) 1000mm – 2000mm+ Schmidt-Cassegrain (SCT) / RC While FOV tells you how much sky you
Tools started syncing directly with capture software like NINA (Nighttime Imaging 'N' Astronomy) and Sequence Generator Pro. Instead of manually copying coordinates, users could frame a target in the calculator and export the exact framing, camera rotation angle, and center coordinates directly into their telescope's sequencing software. Rise of Mobile and Web-Based Apps
If the object spills outside the box, you need a shorter focal length or a larger sensor. To give you an idea of how focal
Mira fed the numbers into her head the way her grandfather had suggested. Focal length 1200mm. Eyepiece 25mm. Sensor width — he’d recommended thinking in terms of what you want to catch: “wide enough to hold a constellation’s arm, tight enough to see its freckles.” With quick arithmetic she found the true field of view, a slender window expressed in degrees. It was little more than a number, but as she traced it in the sky with her finger the backyard became a theater.
I can run the exact field of view math to tell you if they are a good match. Share public link