How to Setup your Tide Clock
TIDE CLOCK OPERATING INSTRUCTIONS
Obtain a local Tide Table and a calendar that shows the days of the full moon, new moon, etc. Some newspapers publish these items, often near the weather report. On the day of a full moon, insert one "AA" (or "AAA" depending on the movement) battery at precisely the time of high tide according to local tide tables. If the Tide Clock is set correctly on the day of the full moon it will display with minimum "error" throughout the entire month. Usually the discrepancy will be less than 30 minutes and therefore will be unnoticeable.
Typically, only four or five days each month will have a difference as great as an hour.
A DISCUSSION OF TIDES
The moon is the major cause of tides. The "lunar day" (the time it takes for the moon to reappear at the same place in the sky) is 24 hours and 50 minutes. Most places have two high tides and two low tides each day. Your Tide Clock has been designed so that its hand rotates once every 12 hours and 25 minutes (twice each lunar day). Your Tide Clock always stays in exact step with the moon. There are many other factors that can make the day-to-day tides a little earlier or later than the Tide Clock shows. It is the user's responsibility to determine these conditions for his own locality and to take them into account. The sun also affects the tides, but less than half the influence of the moon. When the sun, moon, and earth are lined up, as they are at the time of a new moon and a full moon, their influences combine and high tide is higher than normal and low tide is lower than normal. When the sun and the moon are at right angles, as they are at the first quarter and last quarter of the moon, the sun cancels some of the moon's effects and the range of tide is smaller than normal. Also, at these times the sun will make the tides somewhat earlier or later than average. This is why it is so important to first set your Tide Clock on the day of a full moon, as the moon has the dominating effect with the tides.
There are actually two tidal cycles; a twice-daily cycle and a once-daily cycle. On a tide when the two cycles help each other, high tides will be higher and low tides will be lower. On the next tide, when they conflict, the tidal range will be smaller. The relative strength of these two cycles varies from week to week, and also varies from one place to another. In the United States, along the Atlantic Coast the two daily tides have a similar range, but on the northern Pacific Coast there tends to be a large difference between the two daily tides. Farther south and in the Gulf of Mexico, the difference
is so great that there often appears to be just one high tide and one low tide per day. Abnormal atmospheric pressure can temporarily affect the time and height of tides. A difference of one inch in barometric pressure will cause a temporary increase in sea level. Both of these effects will change the times of low and high tides as well. Tides in the lower portions of rivers will be affected by the changing volume of the river flow.