A few words about accuracy

The accuracy requirements are modest: a final position with an error of no more than 1-2 arc minutes (one arc minute = 1/60 degree). This accuracy is in one respect quite optimal: it is the highest accuracy one can strive for, while still being able to do many simplifications. The simplifications made here are:

1: Nutation and aberration are both ignored.
2: Planetary aberration (i.e. light travel time) is ignored.
3: The difference between Terrestial Time/Ephemeris Time (TT/ET), and Universal Time (UT) is ignored.
4: Precession is computed in a simplified way, by a simple addition to the ecliptic longitude.
5: Higher-order terms in the planetary orbital elements are ignored. This will give an additional error of up to 2 arc min in 1000 years from now. For the Moon, the error will be larger: 7 arc min 1000 years from now. This error will grow as the square of the time from the present.
6: Most planetary perturbations are ignored. Only the major perturbation terms for the Moon, Jupiter, Saturn, and Uranus, are included. If still lower accuracy is acceptable, these perturbations can be ignored as well.
7: The largest Uranus-Neptune perturbation is accounted for in the orbital elements of these planets. Therefore, the orbital elements of Uranus and Neptune are less accurace, especially in the distant past and future. The elements for these planets should therefore only be used for at most a few centuries into the past and the future.