Several platforms have become industry standards for their ease of use and extensive equipment databases: Field of View Calculator - astronomy.tools

: While it's a planetarium software, its "Oculars" plugin allows you to enter your gear specs to see a real-time FOV rectangle on the night sky.

He had the gear. A new mirrorless camera with a back-illuminated sensor sat on his desk, capable of seeing in the dark. Beside it lay a heavy, wide-angle lens he had bought during a late-night online shopping spree. But as Elias stared at the star charts on his second monitor, doubt began to creep in. The destination was the high desert—a place known for jagged rock formations and abyssal dark skies. He had one night, one clear window between the waning moon and the rising sun.