Sixty degrees and a narrow allowance
A sextile is a sixth of the circle. The orb here is five degrees, against seven for a trine and eight for a conjunction, and the reason is straightforward. The aspect is considered weak, and a generous orb would put it in most charts and drain it of meaning.
The narrow allowance makes the window ten degrees wide, which the Moon crosses in about eighteen hours at its usual thirteen degrees a day. The sextile occurs twice per lunar circuit, so the total exposure is about a day and a half in twenty seven, giving a frequency near one birth in eighteen. Neptune, at two minutes of arc a day, sits still through all of it.
Neptune retrograde covers close to five months of each year, so most charts carry it and it is not a finding. What is worth noticing instead is the speed gap. Neptune belongs to a generation, the Moon to your birth date, and the contact between them is personal for that reason alone.
An opening rather than a trait
The Moon is instinct, mood and the conditions for rest. Neptune is the softening of boundaries, the imaginative and idealising layer. A sextile joins signs of compatible elements, fire with air or earth with water, and is read as a working connection that stays dormant until something calls on it.
Applied to this pair, the description is an available sensitivity. The imaginative layer is reachable when a person goes looking for it, in a way that a chart without any Moon to Neptune contact would not manage as easily. People with it are often described as good listeners and as comfortable with things that cannot be stated plainly, but only in situations that ask for it. In situations that do not, the aspect is silent and the person may never notice they have it.
This is the honest difference from the trine and the square. The square makes the theme unavoidable. The trine makes it constant and therefore easy to waste. The sextile makes it optional, and optional things in a chart are frequently declined.
Where a small aspect still matters
With only five degrees to work with, the range between tight and wide is compressed. Inside a degree the sextile is worth reading in full. At four or five it is fair to leave it out of a summary altogether, and doing so is more accurate than stretching it.
Element pairing gives the tone. An earth to water sextile reads as imagination attached to practical arrangements, which is the version most likely to produce something visible. A fire to air sextile reads as a facility with atmosphere and suggestion in company. Neither is a prediction, only a description of where the capacity is easiest to reach.
Houses still individualise it and still require the birth time. A sextile touching the fifth or the ninth points the sensitivity at making things or at belief. One between the second and the fourth is quieter and domestic. And as with every aspect in this group, the houses are the only part of the configuration that is genuinely yours rather than shared with everyone born in the same years.
Deciding whether to read it at all
The site's habit is to say plainly when something is minor, and a wide sextile with nothing supporting it is minor. Treating it as a defining feature would be inventing significance, which is the failure this site exists to avoid.
Two situations make it worth attention. The first is a tight orb inside a degree or two, where the description tends to be recognisable. The second is a chart where this is the only contact between the Moon and Neptune and the rest of the chart is hard edged, in which case a small opening onto the imaginative layer is doing more work than its size suggests.
The check above gives the orb, both signs and both houses. With this aspect in particular, look at the orb before anything else, because it decides whether the paragraphs above describe your chart or simply describe the aspect.
Questions people ask about this
Why does the sextile use a five degree orb?
Because it is treated as the weakest of the five major aspects. A wider allowance would put it in the majority of charts and leave it saying very little. Five degrees keeps it meaningful when it does appear.
How common is Moon sextile Neptune?
Near one birth in eighteen. It occurs twice in each lunar circuit but each pass is only about eighteen hours wide, so it is less frequent than the trine or square despite happening just as often.
Is a sextile weaker than a trine?
Generally yes, and in two ways. It carries a narrower orb, and the tradition reads it as a capacity that has to be taken up rather than one already in use. A trine of the same tightness will usually read more strongly.
Does this aspect do anything on its own?
Not much, especially at a wide orb. It is best read as a supporting feature, either when the orb is very tight or when it is the only softening contact in a chart that is otherwise hard edged.
Which elements can a sextile join?
Compatible ones, meaning fire with air or earth with water. That pairing sets the tone of the reading, with earth to water leaning practical and fire to air leaning social and verbal.
Do I need a birth time for this?
For the aspect itself, usually not, since the date settles it. For the houses you do, and the Moon changes house about every two hours. Without them the reading stays generic.