Data
Ephemerides
An ephemeris is a table of positions of celestial bodies for a date. MIRA takes them from the DE440 kernel of NASA's Jet Propulsion Laboratory: the difference from the reference stays within 0.06 arcseconds.
What the table holds
- Ecliptic longitude of every object
- Sign and degree within the sign
- Speed of motion in degrees per day
- A mark for retrograde motion
Accuracy and verification
- Source: the DE440 kernel, covering the years 1550–2650
- Longitudes are apparent geocentric for the epoch of date
- Acceptance threshold: a difference above one arcminute counts as a failure
- Time is calculated and stored in UTC