THIS week, the story of a York genius, his wealthy star-gazing benefactor, a lost invention and the detective work which tracked it down in a foreign land.

Add in elements of a spy thriller and you have a mix which prompts the astronomer's exclamation: "Heaven's above!"

We begin a couple of years ago in a York Astronomical Society lecture. Two members, Martin Dawson and Martin Whipp, are dressed as Thomas Cooke and his son to re-enact the lives of these 19th century optical instruments makers.

It was fascinating, and included details of how they would hunt for a certain breed of spider on Strensall Common. The thread it spun for its web was perfect for creating cross-hatches in telescopic eyesights.

In the audience was another member of the astronomical society, Phil Shepherdson. He makes his own telescopes, even grinding the mirrors himself, so he was particularly taken by the tale of what was then the world's largest telescope.

This necessitates a journey back to London in 1851 and the Great Exhibition, attended by both Thomas Cooke and Robert Stirling Newall.

By then, Cooke was established as a precision engineer of genius. But there had been little in his background to suggest he was destined for greatness. Born in the East Yorkshire village of Allerthorpe in 1807, his father was a shoemaker. Young Thomas only received two years of schooling.

Wanting to do more than cobble, he taught himself maths, navigation and practical mechanics. He made his name with his first telescope and subsequently opened a workshop in Stonegate, York, making spectacles and scientific instruments. He later had premises in Coney Street and then Bishophill, and the firm eventually took over another to become Cooke, Troughton & Simms.

Robert Newall was also a self-made man, only he had made more. His undersea cable-laying business had connected continents and turned him into a very wealthy man.

Newall's hobby was astronomy. While walking around the Great Exhibition in Crystal Palace he encountered the stall of the Chance Brothers, who were glass makers. They were proudly displaying a world's first: two 25-inch glass blanks they had successfully cast.

Newall thought of using them to create a telescope with unmatched prying power. Alas, the glass was not for sale - until he offered the brothers £1,000, an irresistible fortune. Having noted Cooke's presence at the exhibition, he took the blanks and challenged him to turn them into an astronomical telescope.

Here Mr Shepherdson, who has pieced together the details with the help of York astronomer Martin Lunn, takes up the story.

"The project was a daunting one because of the uniqueness of the work and it took seven years to complete. Sadly, Thomas Cooke died before it was finished (possibly because of the stress of it all) so his son continued with the work.

"When it was constructed it became the world's largest telescope in its day. Newall's telescope resided at his Gateshead home for 17 years where it was allegedly used only once or twice.

"The telescope was moved to Cambridge University in 1891 under the direction of Newall's son, Hugh. Increased atmospheric pollution and the advance of modern developments became a major factor in the disuse of this telescope. So, finally, in 1956 it was re-located to the Penteli Observatory at Athens, where it resides to this day."

But no one seemed to know what state the telescope was in. Mr Shepherdson, who works at DEFRA in Kings Pool, York, vowed to go to Athens and track it down. His first attempt ended in failure. But last month he finally rediscovered one of York's greatest exports.

Before travelling, Mr Shepherdson had emailed the director of the Penteli Observatory, Nikolaos Matsopoulos, who quickly agreed to give him a tour. Once over there, our man's mission was jeopardised when he stumbled in the Greek mountains, severely spraining his right foot. But this "was a mission of a lifetime," he says, and was determined to continue.

Now we come to the spy novel moment. The astronomers arranged to meet at a kiosk at a suburban railway station in Athens.

"To aid recognition, I was to carry an English newspaper and wear a blue denim shirt; he would be driving a jeep and described himself as dark, with a beard," Mr Shepherdson recalls. "I was nervous: would my mission be successful? Abruptly I heard a squeal of tyres and a green vehicle came around a corner and stopped alongside me. It was Nikolaos."

They drove up to the observatory. Finally, Mr Shepherdson got to see Thomas Cooke's great creation - the Newall telescope.

It was in perfect condition. Except for a new eyepiece, the nine metre-long masterpiece was just as it had been made in York more than 140 years earlier.

Rediscovering it was a marvellous moment for Mr Shepherdson.

"I had stepped out of this world. It was so magical. There's an air of majesty about it."

The size and design was revolutionary for its day. Newall rarely looked through his telescope, but when he did he may well have seen farther than anyone before him: to the Andromeda galaxy 200 million light years away or close to the surface of Saturn and Jupiter.

The telescope is used to this day. "Even today this achievement in optical size for this type of instrument can only be exceeded marginally, by the 40-inch Yerkes refracting telescope," Mr Shepherdson observes. "However the uniqueness of this Newall telescope is the accessibility of the public to actually observe the stars and planets, at their leisure."

Unfortunately, cost-cutting measures could see the Athens observatory closed and the telescope taken out of use and preserved merely as a museum piece within the next two years. "That would be a crying shame," says Mr Shepherdson.

From his home in Woodthorpe, he is starting a campaign to keep the Newall telescope in use. He plans to send articles to television astronomer Patrick Moore, to specialist magazines and to the Greek authorities. Another trip to the Penteli Observatory beckons at Easter.

After investing so much time and effort tracking down Thomas Cooke's peerless invention, Mr Shepherdson is not about to let it be mothballed without a fight.

Updated: 08:57 Monday, February 07, 2005