How?

The team launched a high altitude helium balloon from Elseworth near Cambridge, England.

The balloon carried a high definition 4K GoPro camera and reached 108,000 feet (20.5 miles) before bursting. It landed near Thetford in nearby Norfolk.

The height of the balloon when the halo was imaged was not precisely known but can be judged from the appearance of the plentiful cumulus way below.

Alec's height for the image at right of the 22° halo and upper tangent arc - somewhat impeded by the same low cumulus - was near to zero. Cambrideshire and the Fens are flat!.

Right below is the flight video. Fasten your seat belt tightly!