  Let $G$ be an almost simple simply connected group over complex numbers. For
a positive element $\alpha$ of the coroot lattice of $G$ let $Z^\alpha$ denote
the space of based maps from the projective line to the flag variety of $G$ of
degree $\alpha$. This space is known to be isomorphic to the space of framed
euclidean $G$-monopoles with maximal symmetry breaking at infinity of charge
$\alpha$. In [Finkelberg-Kuznetsov-Markarian-Mirkovi\'c] a system of (\'etale,
rational) coordinates on $Z^\alpha$ is introduced. In this note we compute
various known structures on $Z^\alpha$ in terms of the above coordinates. As a
byproduct we give a natural interpretation of the Gaiotto-Witten superpotential
and relate it to the theory of Whittaker D-modules introduced by D.Gaitsgory.
