Name: Juan C. Coma
      Teodoro Lopez-Moratalla
      Martin Lara

Title: Fast evaluation of Ephemerides by polynomial approximation 
in the Chebyshev Norm

ABSTRACT:

Computation of planetary Ephemerides can be done from analytical theories 
or from numerical computations. In the second case, fast evaluation for 
the users is provided by polynomial approximations obtained from a data 
base (in our case DE200\LE200). Usually these polyomials have been computed 
using least-squares approximation.  The disadvantage  of this method is the 
absence of an estimate of the error. Another method rarely used is the uniform 
(CHEBYSHEV) approximation. The fundamental advantage of uniform approximation 
is that we bound the error and the maxima and minima values of it are equal 
in absolute value over the entire interval.

We apply the uniform approximation for computing the "Almanaque Na^\tico". 
For an error less than 0.01 arc minute during one month interval, we found 
sufficient using polynomials of degree 7 except for the moon.