Almanac & sky · NUMORA
Mercury Rx Calculator
Heliocentric Kepler minus Earth. Windows good to a few days.
Open interactive calculatorHow to use
Retrograde is apparent longitude decreasing. Not a disaster calendar.
Formula
Daily apparent longitude; Δλ < 0 counts as retrograde
FAQ
Is this Mercury Rx calculator accurate?
The formula and assumptions are shown on the page, and the engine is covered by audit tests. Results are for reference — not financial or medical advice.
Do I need an account?
No. Calculations run in your browser. Recents can stay on this device.
What inputs do I need?
Retrograde is apparent longitude decreasing. Not a disaster calendar.
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