  We study the two-body momentum correlation signal in a quasi one dimensional
Bose-Einstein condensate in the presence of a sonic horizon. We identify the
relevant correlation lines in momentum space and compute the intensity of the
corresponding signal. We consider a set of different experimental procedures
and identify the specific issues of each measuring process. We show that some
inter-channel correlations, in particular the Hawking quantum-partner one, are
particularly well adapted for witnessing quantum non-separability, being
resilient to the effects of temperature and/or quantum quenches.
