Night vision 1.
At night a moments carelessness with a torch or lights below can destroy your night vision in a moment. It then takes about 20 minutes for your eyes to fully adapt to the dark again.
I recently had a student who had a head torch, and whilst they are ideal for doing some tasks, such as working on the engine, he insisted on wearing it on deck. You can imagine the effect this had on everyone else in the cock pit, if you spoke to him he would turn to face you and you would be virtually blind for the next 5 minutes!
Most boats are fitted with red lights to reduce the loss of night vision. These can be very useful for general work around the boat but for detailed inspection of a chart they are not ideal and some of the features can be missed.
One approach if you have to use a light at night is to close one eye during the period that the light is on. This will maintain night vision in that eye; you just need to rememeber which eye to use for dark or light!
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