The calculations have to be right to within half the width of a beam of light.
But, the team of amateur astronomers from Tamworth's astronomy club, in NSW's north east, reckon they can complete the epic refurbishment of a vintage $50 million Baker-Nunn telescope.
The device was designed and built in the 50s to track the Soviet-built Sputnik satellite. It's so old it's difficult to get information on how it functions.
Moonbi's Andromeda Industries director Raymond McLaren admitted fixing the telescope is a daunting task and will take several hundred hours of work.
The hardest part is the hyper-accurate lens.
Lacking accurate data about its shape, the team are using their own measurement gear to to map it so they know what it should look like after they finish grinding it to clean off decades of accumulated gunk.
Project manager Barry Gilbert said the measurement needs to be accurate to literally a handful of microns.
"We've got to measure down to less than a wavelength of light," he said.
"A micron's a millionth of a meter, which is about twice the wave length of light. But we've got other meters there that will measure to about a tenth of a wavelength of light.
"That curve has to be that accurate to form the image.
"When it's polished it has to be a particular shape, roughly a parabola. When we finish it's got to be that same shape."
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The crew aren't scared of all the things that could go wrong, Mr Gilbert said.
"Some of us are just fearless. We don't know enough to know we can't do it," he said.
The team are even inventing some of their own equipment to use in the processes and in the telescope itself.
The device will now be used to search for what are diplomatically called "near earth objects" - the sort of space junk that could slam into the Earth and wipe out humanity.
The telescope has an F1 lens, 800mm in diameter and it's quick, which means it can rapidly get a lot of light with a wide-angle view.
Mr Gilbert said when they first made it they used 70mm film.
"It had 35 degree by 5 degree field of view, which is unbelievable for anything. There's no telescope anywhere that has 35 degree field of view," he said.
"When you take take one shot you've got hundreds or thousands of objects you can look at."
Astronomy club member Phil Betts said the crew are absolute geniuses to take on the epic task.
Mr Betts said the Tamworth club has a "very unique" attitude to its expensive equipment.
"It will allow students and community members to actually use instruments that are first-class in the world," he said.
"For recreation purposes or education purposes. We've talked about working with schools for hands-on education."
The heritage device was donated to the club in January. It had done service at Coonabarabran's Siding Spring Observatory until damaged in a bushfire.
The team estimate the job will take about a year.