The Herschelian Telescope is a reflector telescope design that uses a convex primary mirror and a secondary mirror tilted at a 45-degree angle to reflect light to the eyepiece. This unique design was invented by William Herschel in the 1780s and revolutionized telescope design. While the Herschelian Telescope is the most commonly used name for this type of telescope, there are a few synonyms that can be used. These include the Herschelian reflector, the Herschelian reflector telescope, and the Herschel telescope. No matter the name used, this type of telescope remains an important tool for astronomers worldwide.