Follow this general workflow to plan your next imaging session using an online calculator. Step 1: Gather Your Specifications
By 2021, Astrobin had integrated its massive image database into the FOV calculator. If you searched for "Rosette Nebula" with a RedCat 51 and ASI 183MM, the 2021 tool showed you not just a rectangle, but actual stacked images from other users with that exact rig.
To understand the output of an astro FOV calculator, you need to understand the four primary metrics it uses to calculate your imaging window. 1. Focal Length (Telescope / Lens)
: A simpler, highly visual tool ideal for beginners to see how the Moon or planets look through different apertures. BBC Sky at Night FOV Calculator astro fov calculator 2021
The distance from the primary mirror or lens to the point where light converges to a focus. Longer focal lengths narrow the field of view but increase magnification. Adding a focal reducer shortens this distance, while a Barlow lens increases it. 2. Sensor Size (
Choose a celestial object (e.g., the Orion Nebula) to generate the visual overlay.
Features a fully interactive sky map with real astrophotography overlays (DSS/Telescopius imagery); built-in mosaic planner; saves target lists. Follow this general workflow to plan your next
I can calculate your exact pixel scale and recommend the ideal target matches for your gear. Share public link
Check if your telescope design causes vignetting (dark corners) on larger camera sensors.
Square sensors (like the Sony IMX533) offer identical vertical and horizontal fields of view, making camera rotation less critical. Rectangular sensors (like the IMX571 or full-frame sensors) require careful rotational planning to fit elongated targets like the Andromeda Galaxy. Crop Factors in Astrophotography To understand the output of an astro FOV
The total angular area captured on the sensor.
This formula can be applied to both the horizontal and vertical sides of your sensor. For a camera with a 36mm x 24mm sensor (like a full-frame DSLR) on a 2,057mm focal length telescope: