When sailing at night, especially when tired and trying to identify critical marks in difficult conditions, being able to quickly identify lit marks is essential.
One danger of being prepared by looking up the light sequences in advance, is that it is easy to convince yourself that the light you see is really the one you are looking for!
A good approach is to independently confirm the light has the correct sequence by getting another person to identify it as well. Ideally this person should not know what the chart indicates the correct sequence to be.
When timing a light sequence by counting seconds, always count from the last flash rather than the first one. If you try counting seconds from the first flash you will count one second for each flash. They are not necessarily one second apart!
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