A great refractor was often the centerpiece of a new 19th century observatory, but was typically used with an entourage of other astronomical instruments such as a Meridian Circle, a Heliometer, and Astrograph, and a smaller refractor such as a Comet Seeker or Equatorial.
Heliometer | heliometer |
The first successful measurements of stellar parallax were made by Friedrich Bessel in 1838 for the star 61 Cygni using a heliometer.