Why Your Natal Chart Has No Ascendant or Houses
If you know natal charts, the first thing you'll notice about Synastri's is what's missing: no Ascendant, no house cusps, no rising sign. That's not a shortcut or a bug — it's what happens when a chart is built honestly from a birth date and nothing else.
What an Ascendant and houses actually need
The Ascendant is the zodiac degree rising on the eastern horizon at the moment of birth, and it moves fast — the whole zodiac wheel rotates past it once a day, so it shifts roughly one degree every four minutes. Houses are built from that same rotating wheel, mapped onto the birth location's actual horizon. Both need an exact birth time and an exact birth place; neither can be reconstructed from a date alone. Synastri only asks for a birth date, so rather than fake a rising sign from an assumed hour, it leaves the Ascendant and houses out entirely.
What this chart computes instead
What a date alone is enough for: real sign placements for the Moon and the five visible planets — Mercury, Venus, Mars, Jupiter, and Saturn. Synastri gets these from actual orbital mechanics (the same low-precision Kepler-orbit method astronomers have used for decades, accurate to roughly an arcminute for the Sun and Moon), not a lookup table and not a generic sun-sign horoscope. Every placement is a real ecliptic longitude, calculated for the specific date entered.
The honest tradeoff: no birth time means midnight math
Without a birth time, the chart evaluates the sky at that date's UTC midnight. Most of the time that's close enough — but the Moon moves about 13° a day, so the midnight assumption can be off by up to roughly 6° in either direction, occasionally enough to flip which sign it lands in right at a boundary. The other five bodies move far slower, so they're barely affected. This tradeoff is stated plainly next to the result — not something you have to dig for.
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