The University of Toronto will make an important decision on Tuesday: whether to close down its historic telescope observatory in Richmond Hill and sell the land.

The university says the David Dunlap Observatory, built in 1935, is outdated and no longer useful.

The telescope was once the second-largest in the world and is still the largest in Canada.

Scientist Tom Bolton doesn't want the observatory to close. It was there, in 1971, that he found the first credible evidence of a black hole.

Bolton says he was shocked when he heard that the university wanted to call this site surplus land.

"It took me a couple of days to get back on my feet after that one," he said.

Bolton says the telescope is still useful for his work and it still attracts scientists from Europe.

"I have a research grant proposal due in a few days. I can apply and use other telescopes, but I can't do the same kind of research as I'm doing here," he said.

But the university says cutting-edge astronomy requires a much larger telescope. It also says maintaining the observatory, and the 73 hectares that surround it, costs $800,000 per year.

Pekka Sinervo, the university's dean of arts and science says, "our goal would be to get the largest amount of money for the land in the sale." 

He also points out that the Dunlap Observatory is no longer at the cutting edge of astronomy. "All of the best telescopes now are located at the tops of mountains, because that means there's less atmosphere to see through."

The Town of Richmond Hill would like to buy the land, but can't afford it.

Deputy Mayor Brenda Hogg says the land won't be cheap. "Wild broad guesstimate, start at a half-million [dollars] an acre. Start there," she said.

"For a local municipality, it's an exorbitant amount of money," she said. "The residents would go wild. They don't want to lose it and they don't want to pay for it." 

The university is expected to approve the sale of the land with at least some of it going to real estate developers.