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Tides

Moon phases – new moon, full moon and the two quarters

When is the next full moon, and when was the last new moon? For any date NauticTools2 works out the four moon phases of the current lunation and the following new moon, to the minute in UTC and with no internet connection.

• New moon
• First quarter
• Full moon
• Last quarter
• Next new moon
• Times in UTC

What are moon phases?

The moon orbits the earth and is always lit by the sun. From the earth we see a different part of the lit half, depending on where the moon stands relative to the sun. On the same side as the sun it is new moon. Opposite the sun it is full moon. Between them lie the first and last quarter. One new moon to the next is a lunation, 29.53 days on average.

When do you need it?

• Tides: springs follow new and full moon, neaps follow the quarters. The phases are the starting point for Age of Tide, Tides BSH and Tides ATT.
• Planning night passages: a crossing around full moon is far brighter than one around new moon.
• Anchoring and landfall: if you reach an unfamiliar harbour at night, you know in advance how much moonlight to expect.
• Checking: the calculated times can be compared directly with the moon phases in an almanac or tide table.

The working

• 0° – new moon
• 90° – first quarter
• 180° – full moon
• 270° – last quarter

So the phases are exact moments, not whole days. NauticTools2 searches for the moment the phase angle reaches each value, using the same astronomy library as Ephemeris. It runs entirely on the device and needs neither tables nor the internet.

Worked example

This lunation lasts 29 days, 7 hours and 3 minutes, a little shorter than the average. The new moon of 4 July is the same one the example under Tides ATT shows on the form.

What to watch out for

• Always UTC: all times are in UTC. A phase shortly before midnight may fall on the next calendar day in ship's time. Time Systems helps with the conversion.
• The day starts at 00:00 UTC: the tool works from the start of the date you enter. On the day of a new moon it therefore still shows the previous lunation if the new moon only occurs later that day.
• Last new moon: the new moon at the top always lies before or exactly on the date entered, the other three phases follow it.
• Moon phase is not moonlight: the tool does not say when the moon rises and sets. That is what Rising and Setting is for.

How it works in NauticTools2

1. Open the tool

   The Moon Phases tile opens with today's date and shows the current lunation straight away.

2. Enter a date

   Enter another date, also as six digits such as 070727, and tap Calculate.

3. Save and print

   Save and Load keep a date, New returns to today. The printout contains the input and the result.

Frequently asked questions

How long is a lunation?

29.53 days on average. Because the moon's orbit is elliptical and disturbed by the sun, the length varies by several hours from one lunation to the next.

Why does the app show different times from my calendar?

NauticTools2 gives times in UTC, while calendars usually use local time. Add or subtract your zone difference to compare them.

Do I need an internet connection?

No. The moon phases are calculated on the device, at sea as well and for any year.

Related tools

• Age of Tide – springs, mean or neaps for a date, with a yearly table
• Rising and Setting – when the sun and moon rise and set
• Ephemeris – GHA, declination and other values of the sun, moon and planets