  Very high energy (VHE $>$100 GeV) gamma rays coming from blazars can produce
pairs when interacting with the Extragalactic Background Light (EBL) and the
Cosmic Microwave Background, generating an electromagnetic cascade. Depending
on the Intergalactic Magnetic Field (IGMF) intensity, this cascade may result
in an extended isotropic emission of photons around the source (halo), or in a
broadening of the emission beam. The detection of these effects might lead to
important constrains both on the IGMF intensity and the EBL density, quantities
of great relevance in cosmological models. Using a Monte Carlo program, we
simulate electromagnetic cascades for different values of the IGMF intensities
and coming from a source similar to 1ES0229+200, a blazar with hard intrinsic
spectrum at redshift $z=0.14$, which is an ideal distance for potentially
observing the effect. We study the possible response of a generic future
Cherenkov telescope using a simplified model for the sensitivity, effective
area and angular resolution. Finally, combining these instrument properties, we
calculate the angular distribution of photons and develop a method to test the
statistical feasibility of detecting the effect in the near future.
