“I am by any means no expert, but if I understand the theory we can’t look back any further than this because the earliest universe was a non-transparent cloud?”
They seem to think that they can:
ARE ULTRA-FAINT GALAXIES AT Z = 6; 8 RESPONSIBLE FOR COSMIC REIONIZATION ?
COMBINED CONSTRAINTS FROM THE HUBBLE FRONTIER FIELDS CLUSTERS AND PARALLELS
[....]
We clearly demonstrate here the great potential and the feasibility of peering into the early universe through these cosmic telescopes. The remaining HFF clusters will certainly help improve even more our constraints on the UV LF at z 7 and in particular at z 8 to better assess the role of galaxies in the
cosmic reionization process. Our results also show the
great promise of future programs targeting lensing fields
and pave the way to observing programs with the James
Webb Space Telescope or the Wide-Field Infrared Survey
Telescope (WFIRST), which are scheduled for launch in
the near future.
http://www.spacetelescope.org/static/archives/releases/science_papers/heic1523a.pdf
We shall see when those telescopes go up ...