BBC Sky at Night Magazine

What you’ll need

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▶ A bright, adjustable-focus compact LED torch with a removable lens.

▶ A plastic tube with a length equal to the focal length of the lens plus about 30mm. The tube needs an inside diameter slightly greater than the outside diameter of the torch.

▶ A converging lens with a focal length of 100mm to fit inside the tube.

▶ Mouldable glue to make the lens cell and to cement the tube to the torch.

▶ A saw to cut the tube, a file to deburr the cut end, an abrasive pad to finish smoothing the cut end, and a dowel to shape the inside circumfere­nce of the lens cell.

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