I play a psyker in Dark Heresy 2nd Edition and using mainly the Divination tree. What I want to know is if other characters or NPCs in visual or auditory range can notice that I am using a power, since this does not appear to be specified in the book.
I am aware that there are many powers that are VERY obvious when you use them, but I am more interested in the ones that are potentially discreet (like Divination or Telepathy for example), and I am also aware that another psyker could detect me with Psyniscience. I am mainly after how it works in Dark Heresy but I can accept answers from other W40k RPGs (Black Crusade, Only War etc.) or simply W40k lore.
Best Answer
From a rule point, unless you have a visible effect on the peril of the warp and co. tables, nothing is visible.
From a lore point, most effect have some visible impact, the authors often mention a coldness when calling to the warp. On the other hand some obvious powers like Eisenhorn's command voice has just the uncanny tone and the reaction of most nearby.
As a GM I used to add some low key effect for drama when it had no mechanical impact : if everybody knows what the Imperial Diviner is doing, why not add a little something to the theatrics.