Natal charts establish the reference
A natal chart places the Sun, Moon, and planets at a recorded birth instant. Angles and houses add the local horizon, so they require a reliable time and place. A date-only chart can still show approximate planetary longitudes, but it should not invent an Ascendant. A chart wheel is a drawing of calculated positions; its colors, glyphs, and line thickness are display choices. Keep the data table beside the drawing so readers can see degrees, time standard, and house convention instead of interpreting a stylized picture alone.
Comparison and timing use different inputs
Synastry compares two actual birth charts and measures cross-chart aspects. A midpoint composite derives one set of positions from the two charts, while a Davison chart calculates a sky for a midpoint time and location. A transit chart uses a later real sky against natal positions. A planetary return solves for an exact return to one natal longitude and then draws the sky at that instant. Secondary progressions apply a symbolic day-for-a-year clock. These outputs answer different questions even when each appears as a chart wheel. The result header should name the technique.
Settings can change the picture
Tropical and sidereal zodiacs use different reference frames. Whole Sign, Equal, Porphyry, and Placidus houses can change house assignments without moving a planet's zodiac longitude. An orb controls which angular separations appear as aspects; a wide setting fills the center of a wheel with lines. Optional nodes or other calculated points require a named method. Extra bodies and asteroids should be identified with an ephemeris source and supported date range. Comparing two websites is meaningful only after aligning time, place, zodiac, house system, point set, and orb.
Read the data before the interpretation
A downloadable drawing is useful when its accompanying table preserves input and method metadata. A PDF without those details can make a speculative birth hour look authoritative. Near a house cusp or sign boundary, keep the unrounded degree and check how much the reported time can vary. No chart style proves a psychological description or an event forecast. Treat interpretive text as an authored reading of stated symbols, and return to the original measurements whenever a claim depends on a tight aspect or angle.
Related guides and tools
- Browse independent chart tools
- Calculate a natal chart
- Compare relationship methods
- Compare transits and progressions
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Updated 20 September 2026