Chart settings compared: Aplune and other software
Compare two chart calculations step by step, from birth data to coordinates, houses, divisional charts, and dashas.
In this article
First align the exact instant and location
First verify the local clock date and time, city, historical time zone and daylight-saving conversion. Near midnight, also check whether UTC falls on a different date. Latitude and longitude affect the local ascendant and house cusps; choosing the wrong location or a city with the same name can also cause differences.
Converted UTC and geographic coordinates are the starting point for comparing charts. Once the inputs match, differences in sign placements, divisional charts, and dates can be traced to calculation settings.
Align signs and lunar mansions separately
Aplune’s twelve signs use the tropical zodiac, and divisional charts are calculated from the corresponding tropical positions. Lunar mansions and the starting Vimshottari period use the Dhruva equatorial lunar-mansion method.
Other software may use the Lahiri sidereal zodiac and lunar mansions based on sidereal longitude. When comparing “Indian astrology” settings, check zodiac coordinates, the lunar-mansion reference, and the actual degrees used separately.
Then compare houses, nodes, and divisional-chart rules
Compare whole-sign tables and Campanus cusps separately, and confirm that cusps are being used as center points. For Rahu and Ketu, also check whether true or mean nodes are used.
Divisional charts have different mapping methods. If the original longitudes and D1 match, but a difference appears only in one divisional chart, compare that chart's calculation rules and cusp method.
Finally, compare the initial dasha balance and year length
Confirm the Moon's lunar mansion, its proportional position within it, the nine-planet sequence, the balance of the first period and the year length used for the cycle. This site's Vimshottari uses a Saura year of 365.2422 days. If another tool uses a different year length, date differences may accumulate over time.
Keeping both original outputs and their parameters lets you follow the sequence above to locate the first difference: the Moon’s position, mansion segment, initial period balance or date conversion. The parts that still agree also help narrow the search.
References
- This site’s Calc calculation conventions and provenance; Ernst Wilhelm’s zodiac framework; Swiss Ephemeris and IANA time-zone data.
- Zodiac and lunar mansion conventions used on this site
- IANA: Historical time zones, UTC offsets and daylight saving data
- Astrodienst: Swiss Ephemeris resources
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