They're great to use on an overcast or very cold day in the bush. The trouble is trying to find the deer in the scope once you see a small part of it with the thermal. That takes some practise. There's a few hunters I know who wouldn't bush hunt without one now including myself. Particularly so for bush hunting japs who have a habit of standing behind pepperwoods and such and watching you. Also great in the roar on reds.
They're not much good on a warm or hot sunny day in the bush because all the tree trunks, limbs and any rocks start to give off a heat signature.
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