What is actually in the sky
An opposition is a hundred and eighty degrees of ecliptic longitude between two bodies, with an orb of about eight degrees for a pair including the Sun. When Jupiter opposes the Sun it is on the far side of the Earth from it, which means it rises at sunset, is visible all night and is at its closest and brightest for the year. Astronomers call that opposition too, and for once the two vocabularies mean the same event.
The relative motion is just under a degree a day, so the sixteen degree window lasts around seventeen days, and it recurs every thirteen months or so. Jupiter is retrograde through the middle of it, since retrograde motion is centred on opposition. A natal Sun opposite Jupiter almost always has Jupiter retrograde.
Two bodies, one axis
Read the Sun as deliberate identity, the version of yourself you are consciously building. Jupiter is the urge to widen, to add, to assume there is more available than the current situation shows. Put them at opposite ends of the chart and neither one gets to settle the matter.
The classical description is a person who overshoots and then corrects, in that order, repeatedly. Promises run ahead of capacity. Enthusiasm is real and then has to be paid for. The useful part of the same pattern is that oppositions are visible to their owner in a way conjunctions are not, because the other end is always somewhere across the chart looking back.
Where a conjunction fuses purpose and scale into one impulse, the opposition splits them between two houses and two signs, and the specific pair of houses is the whole story. Second against eighth reads as a lifelong argument about money. Fourth against tenth reads as one about how much of your life belongs to your work.
Retrograde, and why it is not a warning
Because Jupiter is retrograde for roughly four months in each year, retrograde Jupiter is ordinary rather than remarkable, and in this aspect it is close to guaranteed. Interpretations that treat it as a defect are describing a statistical majority.
What retrograde motion does change is the timing of the perfection. A slow pair can perfect more than once when one body turns, and Sun to Jupiter is fast enough that this does not arise, but the same principle matters when you look at transits to the natal axis later. Jupiter will come back to it three times in some years and once in others.
The other point worth being plain about: this aspect is shared by everybody born in a two and a half week stretch. On its own it is background. A birth time puts it on an axis of houses, and that is where it stops being generic.
Reading your own version
Start with the orb from the check above. An opposition inside two degrees behaves like a structural feature of the chart. At seven it is one voice among many and usually loses to anything tighter.
Then look at the signs. Jupiter in Gemini opposite a Sun in Sagittarius is a very different argument from Jupiter in Cancer opposite a Sun in Capricorn, because in the first the scattering happens on the Jupiter side and in the second the restraint sits on the Sun side. Traditional dignity is a rough guide to which end has the upper hand.
Finally, look for a third body. Any planet square to both ends turns the opposition into a T-square and changes it from a dialogue into a problem that demands an answer, which is usually where the real description of a chart lives.
Questions people ask about this
Is Sun opposite Jupiter the same as Jupiter at opposition?
Yes, in the literal sense. When Jupiter is a hundred and eighty degrees from the Sun it rises at sunset, stays up all night and is at its brightest and nearest for the year. If you have this aspect natally, Jupiter was the brightest object in the night sky apart from the Moon.
Why is Jupiter usually retrograde in this aspect?
Apparent retrograde motion happens when the Earth passes an outer planet, and that pass is centred on opposition. Since the aspect only occurs around that pass, Jupiter is nearly always retrograde in a natal Sun opposite Jupiter. It is the normal case and not a flaw.
Is an opposition worse than a conjunction?
It is not worse, it is differently shaped. A conjunction fuses the two bodies so they act as one impulse. An opposition splits them across two houses so each keeps its own territory, which tends to make the pattern easier to notice and harder to ignore.
How wide an orb should I use?
Eight degrees is the standard for an opposition involving the Sun, but the strength falls away quickly. Inside two degrees it is a defining feature. Beyond six it is usually background unless a third planet ties into the axis.
How often does this aspect occur?
The Sun opposes Jupiter a little over once a year, and the eight degree orb keeps it in force for about seventeen days each time. So it is shared by everyone born in that stretch, which is roughly one person in twenty.
What makes one chart's version different from another's?
The house axis, which needs a birth time, the exact orb, and any planet that squares both ends. Those three between them account for almost all the difference, since the aspect itself is common to a whole cohort.