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Photo Ephemeris Web PRO shows when the Moon reaches its maximum and minimum declination in each lunar cycle.
The Moon's orbit is inclined relative to the ecliptic (the plane of Earth's orbit around the Sun) by around 5°. That effect, combined with Earth's own axial tilt of around 23.5° gives us the Moon's declination. As each of these orbits interacts, the Moon's declination moves between varying maximum and minimum declination values over an 18.6 year cycle.
At its greatest, declination reaches a maximum of approximately +28.5° and a minimum of -28.5° - the Major Lunar Standstill, which reaches its next peak in 2024-2025. In between times, we reach the Minor Lunar Standstill, where declinations reaches only +18.5° and -18.5°.
For photographers, the declination of the Moon is an indication of how far north or south the Moon will rise or set. Moonrises which occur near the maximum declination time will occur at more northerly azimuths, and those occurring near minimum declination at more southerly azimuths. This effect is independent of which hemisphere you are in. How far north or south the Moon rises or sets depends on your latitude and the Moon's absolute declination value.
Major Lunar Standstill
At the Major Lunar Standstill, the Moon can be observed to rise or set at its most extreme northerly or southerly points, resulting in some unique lunar alignment possibilities. Additionally, for a northern hemisphere observer, the Moon's transit (when it passes due south) at its minimum declination places it at its lower altitude in the sky, making some photographic juxtapositions possible as viewed from the north which aren't possible at other times in the cycle.
Viewing the Lunar Declination
The Events list shows the date and time of each maximum and minimum lunar declination, along with the calculated value. You can see in the screenshot below, that in May 2024, the declination is close to its greatest possible absolute values.
The timing of these maximum and minima varies with respect to both moon phase and apogee/perigee. The Moon is following three different cycles, each of which has a slightly different 'wavelength'. NASA has an excellent article explaining this in great detail in relation to its consequences for eclipses:
Synodic Month (New Moon to New Moon) = 29.530589 days = 29d 12h 44m 03s Anomalistic Month (perigee to perigee) = 27.554550 days = 27d 13h 18m 33s Draconic Month (node to node) = 27.212221 days = 27d 05h 05m 36s
In the context of the Draconic Month, 'node to node' means the moment when the Moon passes through its 'ascending node', which is the intersection of its orbital plane with the ecliptic, i.e. when declination is 0°, and when the Moon is moving towards its maximum declination.
You can use the events list to quickly evaluate when these different cycles happen to coincide. For example, by December 2024, the maximum declination happens near to full moon. As this is also in the major lunar standstill period, we'll see the Full Moon rising at its extreme northernmost azimuth.
Example
For example, on May 11 2024, in southern Wyoming, the Moon reaches its maximum declination in the early hours. The very next moonrise, a few hours later, occurs at an azimuth of 51°, close to its maximum possible value for this latitude:
Rising Azimuth vs Declination
For an observer at a given latitude, the following table gives the approximate rising azimuth for a body at the given declination. You can use this table to determine appropriate azimuth input values when using Visual Search to find moonrises during the lunar standstill periods. For moonset, the required azimuth is given by subtracting the stated value from 360. For example, for an observer at 40° and the moon at declination +28.5°, the equivalent setting azimuth is (360° - 51.5°) = 308.5°.
Declination ° | ||||
Latitude ° | 28.5 | 18.5 | -18.5 | -28.5 |
70 | UP | 21.9 | 158.1 | UP |
65 | UP | 41.3 | 138.7 | UP |
60 | 17.4 | 50.6 | 129.4 | 162.6 |
55 | 33.7 | 56.4 | 123.6 | 146.3 |
50 | 42.1 | 60.4 | 119.6 | 137.9 |
45 | 47.6 | 63.3 | 116.7 | 132.4 |
40 | 51.5 | 65.5 | 114.5 | 128.5 |
35 | 54.4 | 67.2 | 112.8 | 125.6 |
30 | 56.6 | 68.5 | 111.5 | 123.4 |
25 | 58.2 | 69.5 | 110.5 | 121.8 |
20 | 59.5 | 70.3 | 109.7 | 120.5 |
15 | 60.4 | 70.8 | 109.2 | 119.6 |
10 | 61.0 | 71.2 | 108.8 | 119.0 |
5 | 61.4 | 71.4 | 108.6 | 118.6 |
0 | 61.5 | 71.5 | 108.5 | 118.5 |
-5 | 61.4 | 71.4 | 108.6 | 118.6 |
-10 | 61.0 | 71.2 | 108.8 | 119.0 |
-15 | 60.4 | 70.8 | 109.2 | 119.6 |
-20 | 59.5 | 70.3 | 109.7 | 120.5 |
-25 | 58.2 | 69.5 | 110.5 | 121.8 |
-30 | 56.6 | 68.5 | 111.5 | 123.4 |
-35 | 54.4 | 67.2 | 112.8 | 125.6 |
-40 | 51.5 | 65.5 | 114.5 | 128.5 |
-45 | 47.6 | 63.3 | 116.7 | 132.4 |
-50 | 42.1 | 60.4 | 119.6 | 137.9 |
-55 | 33.7 | 56.4 | 123.6 | 146.3 |
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