A telescope magnification calculator is a tool that calculates the magnification of a telescope based on the objective lens diameter and eyepiece focal length. The formula used to calculate the magnification is:
magnification = objective lens diameter/eyepiece focal length
For example, if the objective lens diameter is 50mm and the eyepiece focal length is 10mm, the magnification would be 5x (50/10 = 5). Keep in mind that this is a simplified formula, and other factors such as the telescope’s focal ratio, the field of view, and aberrations also play a role in the final image quality.