And is the clarity of the Force Ghost as visible to you directly proportional to how much training in using/sensing the Force you have?
In the Original Trilogy, Obi-Wan's ghost only appears to Luke; even when informing someone on Hoth Base of Luke's injury would have been very helpful. Additionally, Obi-Wan is able to appear more 'clearly' to Luke as he progresses in his training.
As such, this made me wonder if one needs to be a trained force sensitive in order to have contact with force spirits? Is there any information on these lines from canon?
Alternatively, is there any canon incidence of Force Ghosts appearing to people who are not trained force sensitives?