When considering if two refractors are both f/10, it is necessary to understand what the f-number means. The “f/10” refers to the focal ratio of the telescope, which is the focal length divided by the aperture. For instance, a telescope with a focal ratio of f/10 will have a focal length that is ten times its aperture in diameter. If two refractors are both listed as f/10, they will share this same focal ratio, meaning they have been designed to gather and focus light in a similar manner, assuming other factors such as aperture and overall design are similar or matched. While both being f/10 implies similar light-gathering efficiency or image brightness under identical conditions, other aspects like optical quality, coatings, build material, and size will affect overall performance and user experience. If you are comparing two refractors to see if they are “same” just based on the f/10 specification, ensure to check these other factors too.