A monumental sundial has been installed in front of the Rio Tinto Alcan Planetarium since last fall. Regulars Planetarium regulars will recognize it from having admired it in front of the previous site, but will now find it has a bit of a different look. In fact, the move from downtown to the Olympic Park was an opportunity to restore it.
The Sun as a clock
The sundial is one of the oldest instruments invented by man. It marks the passage of time using the sun and a gauge (called a gnomon) that can cast a shadow on a graded surface called the dial plate.
A gift that stands the test of time
This sundial was donated to the city of Montreal in 1967 by the citizens of Rotterdam on the occasion of the 325th anniversary of the founding of our city. The dial was created by Dutch sculptor Herman J. van der Heide (1919-1998). The piece is made of steel and aluminum, a happy coincidence now that the Planetarium is associated with Rio Tinto Alcan!
Reliable or not?
It’s often believed, mistakenly, that the Planetarium sundial cannot be functional because its gnomon does not point towards the North Star. It’s true that the aluminum gnomon points to about 15 degrees above the celestial pole. But this does not prevent the Sundial from giving the correct time, because the hour lines on the plate have been drawn in such a way as to compensate for the difference in inclination. However, the dial is fixed at Eastern Standard Time. From March to October, 60 minutes have to be added to the time on the sundial, as Montreal is then on Daylight Saving Time.
Downtown at Olympic Park
The van der Heide sundial remained at the Planetarium at 1,000 Saint-Jacques St. West until it closed. Before relocating to the Rio Tinto Alcan Planetarium, it was restored to its former glory.
A journey through time
Since its installation in 1968, the sundial had been repainted a few times and the dial table adjusted twice. The recent restoration aimed to return the work as close as possible to its original appearance. To eliminate corrosion, the aluminum gnomon was machined with a metal lathe and sanded. The steel structure of the work was stripped, covered with coats of primer and repainted in black. The time plate, meanwhile, has been completely redesigned to match the original conception of the artist. The van der Heide sundial as it appears today in front of the Rio Tinto Alcan Planetarium corresponds exactly to what you, your parents or grandparents might have admired in Chaboillez Square almost 50 years ago...
This text was written with Marc Jobin, astronomer and astronomical information officer at the Rio Tinto Alcan Planetarium.