Sunset is not, as most people think, the time at which the sun disappears and it starts to get dark.

There is an astronomical definition of sunset which is the moment at which the sun’s centre crosses the observer’s rational horizon.

Without trying to explain the complexities of nautical astronomy this means that the time of sunset occurs when, at sea, the sun appears to be about half its own diameter above the horizon.

So it’s going to be light for some time afterwards.

That’s all very well at sea when there’s a good horizon but inland we need to refer to our diaries for the correct time of sunset and add an hour to find the time of the final whistle.

For example the time of sunset today is 18:25pm. As I returned from yet another unsuccessful attempt to catch a salmon the time was 19:10pm and I could still have seen a deer with the naked eye at 200 yards, even with a mist rising over the riverside meadows.

That’s 45 minutes after sunset at a time of year when twilight is much shorter than in the summer.

On many a summer night it doesn’t seem to get really dark at all, so a study of the official time of sunset is mandatory if one wishes to avoid infringing the Deer Act.

As a rough guide, if deer are at all difficult to see you really shouldn’t be trying to shoot them.

That’s responsible, ethical hunting as well as compliance with the Law.