Why Most New Moons Bring No Solar Eclipse: The Tilted Orbit, the Nodes and Eclipse Seasons
The Moon's orbit is tilted about five degrees, so at most New Moons its shadow passes above or below Earth. Only near the nodes, in eclipse seasons that come twice a year, does the shadow land on Earth.
Try it in the instrument
Set the sky to a New Moon with the Moon near Earth and 3 degrees above the plane: no eclipse.
Also called
No other names found in our sources.
A simplified model
The drawings are computed from the numbers in the sources. They simplify the real sky. For exact times and dates, use official tables.
Once a month the Moon lines up on the same side of Earth as the Sun, which NASA describes as the Moon being in the daytime sky. That looks like the perfect setup for an eclipse. Yet most months pass with nothing special in the sky at all.
This guide explains why. The answer is a tilt, and it comes with a few numbers that NASA publishes: the size of the tilt, how close to a crossing point the Moon has to be, and how long the windows for eclipses last. It ends with a task in the Alignment Bench, where you place the Moon too high and watch the shadow miss.
A New Moon every month, an eclipse almost never
NASA says a solar eclipse can only happen at a New Moon, when the Moon is between the Sun and Earth. A New Moon comes about once a month. NASA's glossary gives the length of the synodic month, the time from one Full Moon to the next, as 29.53 days.
Eclipses do not follow at that pace. NASA's Scientific Visualization Studio says the tilt of the Moon's orbit causes the Moon's shadow to miss Earth during most New Moons, about five out of six. The rest of this guide is about what the tilt does.
The tilted orbit
Seen from above, NASA's Scientific Visualization Studio says, the Moon's shadow appears to cross Earth every month. A side view shows why it does not. NASA calls the plane that contains Earth and the Sun the ecliptic plane, and says the Moon does not orbit in that plane. Its orbit around Earth is tilted by about five degrees to it. Fred Espenak of NASA's Goddard Space Flight Center gives the figure as about 5.1 degrees. NASA's Moon fact sheet lists 5.145 degrees.
During a New Moon the Moon usually passes below or above the Sun, NASA explains, and its shadow misses Earth. NASA's video caption says sometimes the shadow is too high above Earth, sometimes it is too low, and other times it is just right, which produces an eclipse.
The two drawings below use the Bench's side view. In the first, the Moon is 3 degrees above the plane of Earth's orbit. In the second, it is 3 degrees below. In both, the shadow passes over or under Earth.
Nodes and eclipse seasons
The Moon's tilted path crosses the ecliptic at two points. NASA's glossary calls them nodes: the two points where a tilted orbit intersects a plane, such as where the Moon's orbit intersects the ecliptic. Near a node the Moon is close to the plane, and that is where an eclipse can happen.
NASA's Scientific Visualization Studio describes how the tilt turns during the year. As the Earth and Moon go around the Sun, the Moon's orbital tilt changes direction relative to the Sun. Sometimes the upper side of the orbit faces the Sun, and sometimes the lower side. Twice a year, for about a month, what faces the Sun is the dividing line between the two sides, the line of nodes. A solar eclipse can only occur at a New Moon that falls within one of those month-long eclipse seasons.
Espenak gives the size of the window. If a New Moon takes place within about 17 degrees of a node, then a solar eclipse will be visible from some location on Earth. The Sun crosses the 34 degree wide eclipse zone around each node in 34.5 days. Because the Moon's cycle of New Moons takes 29.53 days, there will always be one, and possibly two, solar eclipses in each 34.5 day season. Espenak also notes that the actual limit ranges from 15.39 to 18.59 degrees, because the orbits are not perfect circles.
| Quantity | Value | Where it comes from |
|---|---|---|
| Tilt of the Moon's orbit | About 5.1 degrees | Espenak, NASA Goddard |
| New Moon distance from a node for an eclipse | About 17 degrees, in a range of 15.39 to 18.59 | Espenak, NASA Goddard |
| Length of an eclipse season | 34.5 days on average. NASA's glossary gives a window of 31 to 37 days | Espenak and NASA's glossary |
| Time between seasons | Every 173.3 days | NASA's glossary and Espenak |
| New Moons that miss | About five out of six | NASA Scientific Visualization Studio |
| One full turn of the line of nodes | 18.6 years | NASA Scientific Visualization Studio |
NASA says eclipse seasons come twice a year. Espenak adds that the middle of one season is 173.3 days from the next, which is a little less than half a calendar year, because the nodes slowly move westward by 19.3 degrees per year.
How the gaps between eclipses add up
Espenak's table of solar eclipses over 5,000 years shows how the seasons play out. The time between two successive solar eclipses is 1, 5 or 6 lunations, and six is the most common. A gap of six lunations means five New Moons in between that bring no eclipse.
A note on watching the Sun
When a New Moon does bring an eclipse, remember NASA's safety rule. Except during the brief total phase of a total solar eclipse, it is not safe to look directly at the Sun without specialized eye protection for solar viewing. NASA says regular sunglasses, no matter how dark, are not safe. Safe viewers ought to comply with the ISO 12312-2 international standard, and NASA does not approve any particular brand. The guide to watching eclipses safely has the details.
Common mistakes
- Expecting an eclipse at every New Moon. NASA says about five out of six New Moons miss.
- Picturing the Moon's orbit on the same flat sheet as Earth's. It is tilted about five degrees, so the Moon usually passes above or below the Sun.
- Treating an eclipse season as one day. The Sun takes 34.5 days, on average, to cross the zone around a node.
- Thinking eclipses can happen in any month. NASA says there are only two seasons a year when a New Moon crosses the plane and gives a chance.
- Believing the line of nodes stays put. It slowly turns westward and completes a full revolution in 18.6 years, according to NASA's Scientific Visualization Studio.
- Expecting a 3 degree height in the Bench to give a partial eclipse. At that height the shadow misses Earth completely. A partial solar eclipse needs the Moon much nearer the plane.
- Forgetting the twin puzzle at Full Moon. The same tilt matters there too. See why most Full Moons bring no lunar eclipse.
Try it in the instrument
Open the Alignment Bench and set the sky to a New Moon with the Moon 3 degrees above the plane. The correct answer is no eclipse, and the shadow passes above Earth.
- Phase: New Moon. This is the only phase when a solar eclipse can happen, so the Moon is in the right place along its orbit.
- Height: 3 degrees above the plane. The Moon's orbit is inclined about 5.1 degrees. Three degrees is a little more than half of that tilt, so the Moon is well away from a node. Espenak says an eclipse needs the New Moon within about 17 degrees of a node, and NASA's eclipse maps call an eclipse central when the shadow axis passes within 0.997 Earth radii of Earth's center. In the Bench, 3 degrees above the plane is outside both limits, so there is no eclipse.
- Result: the shadow passes over Earth. The task does not name a Moon position, because at this height the shadow misses Earth either way.
Now lower the height toward zero and watch the shadow come down onto Earth. That is the path to the total solar eclipse. The Bench is a simplified model with a range of accepted heights, so it teaches the relation and does not forecast real eclipses.
Questions people ask
Why isn't there a solar eclipse every month?
The Moon's orbit is tilted about five degrees, so at most New Moons the Moon passes above or below the Sun and its shadow misses Earth. NASA counts about five out of six New Moons as misses.
What is a node?
One of the two points where the Moon's tilted orbit crosses the plane of Earth's orbit, the ecliptic, according to NASA's glossary.
How many eclipse seasons are there each year?
Two, according to NASA. Espenak puts the middle of one season 173.3 days from the next, which is a little less than half a year.
If an eclipse happens, will I see it?
Not necessarily. Espenak says that when a New Moon is within about 17 degrees of a node, a solar eclipse will be visible from some location on Earth. NASA says those outside the Moon's shadow will see no eclipse at all.
Sources
- Why Do Eclipses Happen?, NASA Science. https://science.nasa.gov/eclipses/geometry/. Opened November 9, 2026.
- 2017 Eclipse and the Moon's Orbit, NASA Scientific Visualization Studio. https://svs.gsfc.nasa.gov/4324/. Opened November 9, 2026.
- Periodicity of Solar Eclipses, NASA Goddard Space Flight Center, Eclipse Web Site (Fred Espenak). https://eclipse.gsfc.nasa.gov/SEsaros/SEperiodicity.html. Opened November 9, 2026.
- Eclipse Glossary, NASA Science. https://science.nasa.gov/eclipses/glossary/. Opened November 9, 2026.
- Key to Solar Eclipse Maps, NASA Goddard Space Flight Center, Eclipse Web Site (Espenak and Meeus). https://eclipse.gsfc.nasa.gov/SEcat5/SEmapkey.html. Opened November 9, 2026.
- Moon Fact Sheet, NASA Space Science Data Coordinated Archive. https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html. Opened November 9, 2026.
- Eclipse Viewing Safety, NASA Science. https://science.nasa.gov/eclipses/safety/. Opened November 9, 2026.
We opened each source ourselves on the date shown. The drawings are our own and were checked against the numbers in these sources.
Read next
Unlock this guide
Play one round for this entry to unlock the full guide, or unlock it now without playing. The choice is saved in this browser only.