The observatory was founded in 1826, and fitted out with its first set of refracting telescopes in the 1860s. These instruments are now part of the University of Aberdeen's historical collections. For many years the main use of the observatory was meteorological rather than astronomical. Due to structural deterioration, it has not been in use since the 2000s.
The history of astronomy at Aberdeen goes back some 400 years, and the CTO itself has a long and interesting history. Both the history of astronomy at Aberdeen and the CTO in particular will be expanded upon elsewhere on the Physics website. For now, you can read a history of the CTO at John Reid's webpages.
Layout
The observatory consists of two observing domes. In this photo, taken by drone, the two cone-shaped domes at the bottom are on the roof of the CTO. The south dome is on the left and the north dome is on the right.
This photo shows the interior of the CTO as it appeared in October 2025. The north dome is on the left, the south dome is on the right, and the entrance is on the far side. The viewing slit in the south dome is open.
Within the observatory, there is a circular observing platform for each dome, which instruments can be mounted on. These extend from the floor up to about 2.7m height (the south dome platform is slightly lower), at or just below the roof. Surrounding each platform is a circular pier that observers can stand on, approximately 1.5m above the level of the room, which is accessible by steps. These images are scale drawings of the interior made around 2000 by the Aberdeen Astronomical Society (AAS).
2000s refurbishment
By 2000, the only telescope to have been under the domes in recent years was a simple 8" reflecting telescope. In June 2000 a refurbishment programme led by Dr John Reid began, aiming to bring the observatory back into astronomical use with up-to-date reflecting telescopes.
This was no easy undertaking as a lot had to be done to make the observatory suitable for use. The images show the interior of the CTO before refurbishment started. The first task was to empty the room entirely, which involved sifting through and clearing out hundreds of journals and papers left by previous users, moving old equipment, dismantling furnishings, and so on. Contractors were then called in to fix the roof and windows, lubricate the observing domes, and redecorate the interior.
Unfortunately, however, the observatory was found to have a persistently leaking roof. To repair this, along with the rest of the CTO and the roof stairs, would be prohibitively expensive. Other difficulties included risks of structural damage due to prolonged water exposure, the CTO being unsuitable for modern accessibility requirements, limited space to install larger modern telescopes, and floodlighting installed to illuminate King's College facade, which has affected the quality of astronomical observation and considerably reduced the usefulness of the observatory.
Image credits (from top): Dr Roland Young; Timothy Wang; Dr Roland Young, Aberdeen Astronomical Society; Dr John Reid (x2); Christopher Willett (x3); Dr John Reid.