Thieves have stolen more than £10,000 of star-gazing equipment from Todmorden Astronomy Centre.
Two specialist pairs of binoculars and a unique, hand-made telescope used to view the sun are among the 15 items stolen.
The theft occurred some time between Friday April 27 and the next day.
A £1,000 reward is now being offered for information leading to the return of all the equipment.
A pro-rata sum will be paid for individual items recovered.
Peter Drew, who opened the centre as a resource for amateur astronomers and the public, said the whole astronomic society was on the lookout for the stolen equipment after alerts on several websites.
“There are hundreds of people throughout the country looking for these items,” he said.
“I’m just hoping they turn up undamaged. The telescope is used to look directly into the sun and I made it myself so it’s a unique piece of equipment.
“It’s hard to say whether the people who have taken it knew what they were taking.
“But they were certainly prepared because some of the equipment they have taken was quite big and they will have needed a van to take it away.
“We’re open on Saturday from 7.30pm for the public to come in and you just don’t know who is coming in and having a look around at what is here,” he said.
“I would normally have been at the centre during that week but I wasn’t well so I didn’t go, so it is hard to give an exact time when it happened,” he said.
The stolen equipment includes a six-inch F8 refracting binocular telescope, a 12-inch Meade LX200 OTA, a six-inch F8 black Helios refractor modded Ha scope, a six-inch F8 blue Skywatcher refractor, three Coronado PST bodies and two black EQ6 mounts and one white EQ6 Pro mount.
Police are asking anyone who can help in recovering the items to contact police on 101.