In infinite space and time, there is only one Hampstead Observatory.

Set atop a reservoir on the highest spot in the capital, the 102-year-old Victorian wooden building has survived two world wars, land grabs by property developers and a rise and fall in the popularity of astronomy.

Though set up in 1899, the observatory was built in 1910 and the society’s members still stick to its guiding principle of free education to the public.

To this day it is the only observatory in London which is regularly open to all and operates free of charge.

Ex-plumber Simon Lang, assistant astrological secretary, said: “It all stems from that Victorian ethos of the wealthy taking it on as a responsibility to society and we are still doing that today, helping to educate people about astronomy.

“People are often very intimidated by science, the fear of the unknown and the fear that it’s all too much, but it’s not and we really want to promote that feeling.”

The Hampstead Astronomical and General Scientific Society was formed on the back of the enthusiasm of amateur astronomer P. E. Vizard and generous benefactor Colonel Henry Heberden, who was armed with a 10.5inch telescope and a desire to donate it to a good cause.

With a little help from then Ham&High editor John Hayns, the enthusiasts secured a spot of land on Hampstead Heath near Highgate Men’s Pond to set up the telescope.

However, the lack of street lighting and the relative obscurity of the location meant initial enthusiasm for stargazing in the area tailed off and the society was forced to relocate to its current site off Lower Terrace in the heart of the village.

With the agreement of the water board, the society installed a stone plinth which spirals all the way down into the reservoir and where the observatory’s telescope is mounted to this day.

The ingenuity of its members has been a hallmark of the society since its inception, with long-time member Henry Wildey using fabric from a Second World War barrage balloon to line the inside of the dome.

Now volunteers are undertaking serious repair work which will guarantee the building’s future.

Today the society suffers from the light pollution of the capital which limits the 1928 telescope’s ability to search out the entire skyscape.

On a clear night, however, stargazers can still be dazzled by the sight of a wispy ring of a nebula and a neighbouring Andromeda galaxy can be spotted more than two million light years away.

“For young people this is far out of their experience,” said Mr Lang, a member since the early 1980s.

“They are blown away by it and that’s why it is crucial to keep it as it is for another 102 years.”

The observatory reopens on October 19.