Leiden Heliostat

Heliostaat Oude Sterrewacht LeidenHeliostaat Oude Sterrewacht Leiden SchetsHeliostaat Oude Sterrewacht Leiden solar imageHeliostaat credits

The Heliostat is a solar telescope, designed specically to track the sun and project a 90-cm image of it on the wall inside the Old Observatory visitors center. The light travels from the roof through the old chimney of the director's office to the visitors center down below. (Oort's and De Sitter's chimney.)
This telescope was initiated in 2014 by the committee working on the new exhibition, mainly since in March of 2015, an 84% solar eclipse would take place in the Netherlands. To raise the money in time, it was decided to use crowdfunding, which worked fantastically. The required €20,000 was raised within a month and building could commence. Using a bare bones approach it was possible to install the critical parts in time for the eclipse. Later, a dome and other protective elements were added and the telescope was officially unveiled by the Rector Magnifcus, Professor Stolker just in time for the Mercury transit of May 2016. Ever since, the telescope has projected a solar image on a wall in the visitor's center whenever the weather permits.
Afer the telescope was completed, two students decidcied to expand upon it as part of their bachelor research project. This resulted in a spectrograph that can measure the Sun's rotation when placed on one of the edges by using the Doppler effect. This instrument is now used for student practicals and is in ongoing development for public use.

The designer of the dome lovingly called it a 'motor helmet', due to the unorthodox shape. However, to his dismay, the name that stuck was the 'Baby carriage'.

About the telescope

D = 10 cm
f = 100 m
Scheifspiegler design


From attics to domes, Four centuries of history of Leiden Observatory. (2018) ISBN: 978-91-639-7671-1
Photo's of the project being done

Last update 7/12/2018 by Alex