Best for: Deep session planning, target discovery, and advanced mosaic planning.
Stellarium is a free, open-source planetarium software available for desktop, mobile, and web browsers. By clicking the "Oculars" plugin icon in the top right corner, you can input your telescope and camera sensor specifications.
Use a calculator to plan 3-4 eyepieces that cover these FOV ranges:
To help find the perfect tool for your current setup, let me know: What and camera models do you currently use? What specific deep-sky target are you trying to frame?
Before diving into the tools, it helps to understand the math and physics happening behind the screen. Your Field of View determines the window of the sky that your camera sensor can capture through an optical system. It is dictated by two main components: 1. Focal Length (The Telescope/Lens)
Ignoring exit pupil. An FOV calculator won’t warn you if your eyepiece creates an exit pupil >7mm (wasting light) or <0.5mm (floaters become visible). For visual use, keep exit pupil between 0.7mm and 6mm.
A good FOV calculator solves all of this by computing two critical numbers: and Apparent Field of View (AFOV) .
Long focal lengths with tiny pixels lead to blurry images due to atmospheric seeing.
For cameras, the FOV is determined by the telescope's focal length and the size of the camera's sensor. Using the sensor's dimensions, you can accurately calculate your field of view: FOV (in degrees) = 2 × arctan(Sensor Size / (2 × Focal Length))