Fraunhofer and the Great Dorpat Refractor

The Great Dorpat Refractor built by Joseph Fraunhofer and completed in 1824 was the first modern, achromatic, refracting telescope. At the start of the 19th century, progress in astronomy was stifled by the lack of astronomical quality telescopes of sufficient aperture and manageability. There were long-focus, nonachromatic refractors, reflectors with speculum metal mirrors, and achromatic refractors of small aperture and mediocre design. Contributing to the construction and success of the Great Dorpat Refractor were P. L. Guinand's development of a process for making large disks of homogenous flint glass, Fraunhofer's improvement of the design and fabrication of the optical and mechanical components of the telescope, and F. G. W. Struve's skilled and dedicated use of the telescope and its accessories. The successors of the Great Dorpat Refractor were the giant refractors which were the mainstay of astronomy in the 19th century and which were not displaced until the early 20th century when the age of the giant reflectors began.