7 min · Goal: Verify that a computed chart is correct before interpreting it.
Two sites can give different charts for the same birth details, and the difference is almost always one of four settings rather than a bug.
Ayanamsa. Lahiri is the Indian standard, but Raman, Krishnamurti and others differ by up to a couple of degrees. Usually too small to change a sign, occasionally enough to move a planet across a boundary.
House system. Whole sign is standard in Indian practice. Placidus and others place cusps inside signs, so a planet can be in one sign but a different house.
Timezone and daylight saving. The commonest source of error by a wide margin, especially for births in countries that used DST historically and inconsistently. India has not used DST since 1945, but diaspora births frequently do.
Node calculation. Mean versus true node differs by up to about a degree and a half. Most Indian practice uses mean.
Compare two independent calculators. If the Lagna matches, the time and place were handled the same way. If planetary longitudes match to within a degree, the ayanamsa agrees.
Sanity-check the Moon: it moves about 13 degrees a day, so if two sources disagree by more than that, one has a date or timezone error rather than a settings difference.
Check that Rahu and Ketu are exactly 180 degrees apart. If not, something is wrong.
And check the dasha balance is consistent with the Moon’s position — the Level 6 calculation takes two minutes by hand and catches errors that propagate through everything else.
Any tool worth trusting will tell you its ayanamsa, house system and node convention. If those are not stated anywhere, that is information about the tool.
For the record: this site uses Lahiri ayanamsa, whole sign houses, and computes positions with a VSOP87-based astronomical engine rather than lookup tables. The AI writes interpretation only and never generates a number.
Two sites give Moon positions 4 degrees apart for the same birth. Settings difference or error?