The angle, the orb and the timing
A conjunction is the two bodies at the same ecliptic longitude, with eight degrees of orb allowed either side. Neptune advances roughly two minutes of arc a day, which is slow enough to treat as motionless. The Moon covers about thirteen degrees a day, so it crosses the whole sixteen degree window in a little over a day, once in every twenty seven day circuit.
Frequency lands near one birth in twenty two. What makes it interesting is the contrast with the rest of the Neptune column. Sun, Venus and Mars all move about a degree a day, so their conjunctions with Neptune hold for well over a fortnight and are shared by everybody born in that stretch. A Moon conjunction turns over in hours, which makes the birth date decisive and the birth time necessary for the house.
Neptune is retrograde for roughly five months of every year. A natal retrograde Neptune is therefore the ordinary case, present in a large share of charts, and it says nothing on its own.
The two bodies, fused
The Moon signifies instinct and need, the level at which a person reacts before deciding, along with memory and the conditions for rest. Neptune, in the interpretation built up since its discovery in the nineteenth century, signifies dissolution of boundaries: imagination, idealisation, the blur between what is and what is pictured.
A conjunction fuses rather than balances, and the fusion here is between the reflex layer and the softening one. The standard reading is a person whose emotional responses are unusually permeable. Other people's moods arrive as if they were their own, and the line between empathy and absorption is not clearly drawn. Sensitivity to atmosphere is high, and so is the tendency to fill in missing information with something more appealing than the facts.
Older sources attach both artistic capacity and self deception to this aspect. They are one mechanism seen from two sides, and the chart cannot say which you get. It describes a weak filter, useful in some settings and costly in others.
Orb, house and what sharpens the reading
Orb decides how much of the description applies. Inside two degrees this is a genuine structural feature and tends to be recognisable. Between five and eight it is a mild colouring, and a conjunction that straddles a sign boundary, with the Moon in the last degrees of one sign and Neptune in the first of the next, loses most of what the classic reading assumes.
House is the individualising factor and requires an accurate birth time, since the Moon changes house about every two hours. In the fourth this reads through home and family and is where the absorption is most often described. In the tenth it points at a public role that is easier to project onto than to define. In the twelfth it doubles the theme, and in the sixth it usually shows up in health and daily routine rather than in anything obviously imaginative.
Sign adds texture. In Pisces the pairing is at home and reads as unremarkable in a chart that already leans that way. In Virgo or Capricorn it sits against the grain and tends to be more noticeable to the person, because the rest of the sign's preferences keep asking for a clarity the conjunction will not supply.
Keeping the claim the right size
Neptune attracts more overstatement than any other body in the chart, and it is worth resisting. This aspect does not make anyone psychic, an artist, or an addict. It describes a low resistance at the boundary between self and surroundings, which is a modest and testable claim about disposition and nothing more.
It also matters what else is in the chart. A Moon conjunct Neptune in a chart with a strong Saturn is a very different arrangement from the same conjunction with nothing structured anywhere, because the permeability then has something holding shape against it. Read the pair, not the aspect alone.
The widget above returns the orb, the shared sign and the house. Those three facts are what separate a real reading from a general description, and with this conjunction the orb in particular tells you whether the paragraphs above are about you or about somebody with a much tighter aspect.
Questions people ask about this
Is Moon conjunct Neptune a generational aspect?
No. Neptune is generational, sitting in one sign for about fourteen years, but the Moon passes it once every twenty seven days. The contact itself lasts around a day, which makes it personal to your birth date.
How long is the window for this conjunction?
A little over a day. The orb is eight degrees either side, so the window is sixteen degrees wide, and the Moon covers about thirteen degrees every twenty four hours while Neptune barely moves.
Does this aspect mean I am psychic?
That is a common claim and the chart does not support it. What the tradition describes is a permeable boundary between your own moods and the atmosphere around you. How that gets interpreted says more about the interpreter than the aspect.
My Neptune is retrograde. Does that change anything?
Not meaningfully. Neptune spends about five months of each year in apparent retrograde motion, so most charts have it retrograde. It is the ordinary case rather than a signal worth reading.
What if the conjunction crosses a sign boundary?
It weakens considerably. The classic reading assumes both bodies in the same sign, so a Moon at twenty eight degrees of Aquarius with Neptune at three degrees of Pisces has the geometry but very little of the effect.
Which house version is strongest?
The fourth and the twelfth are the two most often written about, since both already carry themes of interiority and family. That is a matter of interpretive convention rather than evidence, and the sixth or tenth versions read quite differently.