Night vision goggles, monoculars and binoculars that let you see what happens after the sun goes down. Digital infrared kit from Nightfox, priced from £79.99 inc. VAT, plus thermal imaging when you need to spot heat rather than light.
Start with what you are actually looking at. Digital night vision, which is everything in the Nightfox range here, uses an infrared illuminator to light the scene and a sensor to show it on a screen. It gives you a clear picture in true darkness and it is the sensible choice for badger watching, checking on livestock, night walks and airsoft. Thermal, like the Thermal Master DV2, works differently. It reads heat, so it finds a deer in undergrowth or a fox across a field that digital IR would never pick out. It costs more for a reason.
The other choice is how you hold it. Monoculars like the Prowl and Prowl 2 are one-eyed and light, so they slip in a coat pocket and are easy to lift and lower. Binoculars like the Ember and Whisker are more comfortable over a long sit, since both eyes stay busy and you get a better sense of depth. The Swift 2 and Swift 2 Pro are the goggle-style option for hands-free use.
Check the stated IR range against your ground before you buy. A garden needs far less reach than an open field.
For everyday darkness, see Torches & Headlamps, and browse Camping & Field Gear for the rest of the night kit.