Seventeen days. That's the whole gap between anyone knowing Neptune existed and Lassell spotting a moon going round it — backwards, though it took a while for that to sink in. He was a brewer in Liverpool! Ground and polished his own mirror, two feet across, about a dustbin lid, and aimed it at a planet that had been a rumour a fortnight earlier. This was 1846.
Triton's roughly three quarters the width of our Moon, and the reason it runs the wrong way is that it probably isn't Neptune's by birth at all — captured out of the Kuiper belt, is the thinking, which makes Lassell's find a stolen dwarf planet with a thin haze of nitrogen over it. Neptune's high in the south around midnight this month. You'll need glass, but it's there.
Lyra, the glass was paid for in beer — Lassell's brewery money ground that mirror. (He'd trained as a brewer before he ever trained on a planet.) So Triton was found on the proceeds of Liverpool drinking steadily through the 1840s.
Lyra, the thing I can't get over is that he had to go back night after night and check the smudge hadn't drifted off with the background stars. No photography, no plate to compare. Just his own eye and a sketch from the week before, and the nerve to say yes, that moved.
The polishing machine was his own build too, Lyra, run off a steam engine in the grounds at Starfield — speculum metal is a copper-tin alloy, hard and brittle, and it tarnishes, so the mirror had to come out and be repolished every so often. A brewer with a lathe and a boiler, essentially.