eta values

[p g duncan <p.g.duncan@durham.ac.uk>]

Dear All,

I am using PARI/GP 2.1.3 on Solaris and am getting what appear to be 
inconsistent results for [eta_1, eta_2] from an elliptic curve.  I type

? E = ellinit([17, -57, -103, -117, -59]); E.eta 

%1 = [-2.807956857452822888489521845, -8.483106191227845728912379030*I]
? E.omega
%2 = [0.5129665050097666315838565943, 0.4309028743584948650112829254*I]
? elleta(E.omega)
%3 = [-8.965528371164577009721846459 + 0.E-27*I, 0.E-27 + 
4.717488058710698207080157472*I]

Why is elleta(E.omega) different to E.eta?  Should not both give the 
quasi periods of the Weierstrass Zeta function defined on the lattice 
for which E.omega is a basis?

Thank you in advance for your help.

Yours sincerely,

Paul Duncan