Caption: William Herschel (1738--1822) (one assumes) and his 0.48-m reflector a Slough, England near Windsor Castle (see also No-400).
Features:
However, the scaffolding being aligned with celestial meridian only allowed limited east-west slewing.
However, astronomical objects within the north-south range transit the meridian daily and so can be observed for some short time by the limited east-west slewing.
Reflectors have advantages which would cause them to win out as the dominant telescope after circa 1900. Some of these advantages were appreciated by Herschel: it is easy to make large reflectors (compared to making large reflectors) and reflectors don't suffer from chromatic aberration instrinsically.
Speculum is an alloy of copper and tin with a dash of arsenic---which gives that je ne sais quoi---invented for reflector telescope mirrors by Isaac Newton (1643--1727).
It is brittle, tarnishes easily, and reflects only about 16 % of incident light.
Newton also constructed the first working reflector telescope in about 1668 based on earlier ideas by Scottish mathematician and astronomer, James Gregory (1638--1675) published in 1663 (North 1994, p. 347).
But the 1.26-m telescope had one great achievement. It was used to discover the 6th satellite of Saturn, Enceladus.
Credit/Permission: Anonymous artist,
later 18th century /
Public domain.
Download site:
Wolfgang Steinicke's List
of NGC/IC observers