Degrees decide aspects, not membership
An aspect is an angular distance between two points, and the traditional set are simple fractions of the circle: the opposition at one hundred and eighty degrees, the square at ninety, the trine at one hundred and twenty, the sextile at sixty. Whether two bodies form one depends on their degrees, not on their signs.
A Sun at seventeen degrees of Leo makes an exact trine to anything at seventeen degrees of Aries or Sagittarius, and an exact square to seventeen degrees of Taurus or Scorpio. Move it five degrees and those relationships loosen or disappear while the sign name stays identical. That is the practical reason to know the figure.
Signs still matter to aspects in the traditional scheme, since an aspect between signs of the same element or mode was treated as smoother than one that crosses them. The degree decides how exact it is, and the sign decides its character.
The figure for this date
At noon across every year from 1930 to 2035, the Sun on 9 August has stood between roughly sixteen and about seventeen and a half degrees of Leo. The spread across the century is small because the leap day cancels the quarter of a day the calendar loses annually, holding the date against a fixed solar longitude.
Within a single year, a birth just after midnight falls at the bottom of the day's range and one late in the evening near the top, a difference of well under a degree. For aspect work that is not negligible, which is why the year, the hour and the place all belong in the calculation rather than a published range.
The lowest figures in that window fall in leap years and the highest three years afterwards, repeating on the same four year cycle that governs every date.
Orbs and how close is close enough
Exact aspects are rare, so practice allows an orb, a margin either side within which the aspect still counts. Different schools use different figures and the Sun is usually granted a wider one than the smaller bodies, often somewhere between six and ten degrees for the major aspects.
That is a convention rather than a measurement, and it is where two competent astrologers most often disagree about the same chart. It also means the century wide window for this date can matter: two people born on 9 August in different years can have a planet inside orb for one of them and outside it for the other.
Wider orbs catch more contacts and narrower ones fewer, which is a choice of method rather than a fact about the sky.
The band, and what the date leaves out
Seventeen degrees sits in the second of Leo's three ten degree divisions, ten to twenty, assigned to Jupiter under the Chaldean order. The tradition reads that band as the sign's warmth given room, inclined to teaching and to hosting, which is inherited convention rather than a finding.
None of the aspects themselves can be worked out from a date, because the other bodies depend on the year and the houses on the hour and place. The widget above computes the exact solar degree for a given birth, along with the distance from the nearest sign boundary, which is the starting point for the rest.
Put together, a date supplies the Sun and its band and stops there. That is a smaller claim than most birthday pages make, and it has the advantage of being true.
Questions people ask about this
Why does the exact degree matter if the sign is settled?
Because aspects are measured in degrees. A Sun at seventeen degrees of Leo forms an exact trine with seventeen degrees of Aries or Sagittarius, and shifting it a few degrees changes which contacts are close.
What is the Sun's degree on 9 August?
Between about sixteen and roughly seventeen and a half degrees of Leo at noon, depending on the year. The widget above returns a single figure from a year, an hour and a birthplace.
What is an orb?
The margin either side of an exact aspect within which it is still counted. The figure is a matter of convention and varies between schools, with the Sun usually allowed a wider one than the smaller bodies.
Which decan is 9 August?
The second decan of Leo, from ten to twenty degrees, which the Chaldean order assigns to Jupiter. The whole noon range for this date sits inside that band.
Can two people born on the same date have different aspects?
Yes. The other bodies move on their own cycles, so the year decides almost all of it, and even the Sun's own degree differs slightly between years and between hours.
Is 9 August ever a sign other than Leo?
No. The Sun is more than halfway through the sign on this date, well over a week from the move into Virgo, so the sign holds in every year and at every hour.