The Field of View is the angular size of the sky visible through your imaging system.
Live-stackers need real-time FOV feedback to centre targets without wasted slew time. Hot integrations now link FOV calculators directly to plate-solving software, so your calculated preview matches the sky to sub-pixel accuracy. astro+fov+calculator+hot
Leo opened his planetarium software (Stellarium) and overlaid the image. The hot pixels acted as a dummy star field, showing him exactly how his sensor was oriented relative to the sky. He realized the calculator had been wrong—or rather, he had misjudged the spacing of his field flattener. The Field of View is the angular size
The calculator had given him the theory, but the "hot" pixels had given him the truth. astro+fov+calculator+hot