Has it ever been canonically (or beta canonically) established as to what distance Betazed telepathic abilities can work? I ask as I’m writing a fanfic with a part Betazed original character (Maternal grandmother was Betazed).
Well, there were those times when Troi could tell that somebody they were communicating with on another ship was lying. And in NEM she telepathically detected the Reman Viceroy on the Scimitar, from the Enterprise bridge. Kor
So our options are "a couple of hundred kilometers" and "as long as the range of comms, aka infinite". The latter would sound likelier if we got any evidence at all that range mattered. If, say, it were harder for Troi to read somebody six cabins away than people sitting next to her, then it would be really unlikely for her to be able to read somebody a hundred klicks away - in which case she would "instead" be reading the image that is right next to her. And it then wouldn't matter if the image came from three galaxies away. And she could read recordings and photographs, too. Alas, we really don't learn of it being more difficult to read somebody six cabins away. Or of Troi fluently reading photographs. With distant people, it's apparently more like an issue of nearby ones drowning out the telepathic signal. And "Tin Man" makes that, too, sound more like a case if selectively switching off certain inputs and focusing on others, rather than distance mattering. Yet "Tin Man" also shows Tam Elbrun reading the Romulans, who don't communicate, from across thousands of kilometers at least, and being in contact with Tin Man across tens of thousands (although the latter may be more thanks to the living starship than the Betazoid). Is Tam special when it comes to range, too? Timo Saloniemi
https://memory-alpha.fandom.com/wiki/Betazoid Most developed their telepathic skill in adolescence, but a few were born with their telepathic abilities already active, such as Tam Elbrun. (TNG: "Tin Man") These individuals were almost always extremely talented and powerful in telepathic terms, but also unable to screen out the consistent noise of other people's minds, so they generally suffered mental problems of varying severity depending mostly on when the problem was diagnosed. On the other end of the scale were a few individuals who developed psionic abilities that were far below average for the species (for example, Lon Suder). Those Betazoids were barely able to sense even strong emotions (empaths) of other people, much less thoughts.
Yup, we know Elbrun is special. We aren't told anything about his range of abilities, though. And that includes the range of his abilities. Timo Saloniemi
Also, for OP, "Betazed" is the name of the planet. While the people were referred to as "Betazeds" a couple times in TNG, it is much more typical to call them "Betazoids." Kor
It took a while to see this in onscreen writing, so there was a bit of ambiguity over whether the "proper" name of the place might in fact be BZ, that is, beta-zed, straight out of some human stellar catalogue (with the native name never being heard)... Actually, that ambiguity still remains, here and in most such cases. At least we know that "Romulan" is a native Romulan term (ENT "Minefield"), but "Vulcan" might well be pure Earthspeak! Thankfully enough, the folks never were "Betazedians" or "Betazedites". "Beezees" or "Betas" might have had the right buzz to it, tho. Timo Saloniemi
We know that Elbrun and his type have "Longer Range" than average Betazoids, but how much longer is up to interpretation based on on-screen evidence.
Hmh? The episode tells us that Elbrun has "extraordinary talent", is a "unique person", "very high on the ESP scale", a "prodigy" of sorts, "the Federation's finest specialist in communication with unknown lifeforms", and "can hear everything everybody on the ship is thinking". We then learn he is in something of a contact with Tin Man across a range of "lightyears", which Troi declares "impossible even for you". Elbrun actually agrees, and suggests it's Tin Man doing the contacting. Nothing concrete there about "his type" having great range as such, or even existing (Elbrun is "unique" even if only as a person). Perhaps these prodigies have longer range than usual Betazoids, perhaps not. Certainly range as such is a factor, both because of the "lightyears are impossible" thing, and because Elbrun did find solitude when traveling to suitable locations. But this range may be the same for all Betazoids as far as we can tell. His ability to read the Romulan commander in the passing, when Troi could not, unfortunately tells us nothing, since Troi can't read minds and isn't a Betazoid... Alas, we never heard of her mother reading the commanders of passing starships that way. Or denying that she could do so. Timo Saloniemi
We had episodes were Troi could even sense the emotions of people on a planet while the ship was in orbit (the Bonding) And that's, in my opinion the biggest reason why many writers struggled with Troi; her ESP abilities, and their limitations, were never properly defined anywhere.
There is consistency of sorts in that very thing: Troi gets to sense more when those being sensed are powerful and noisy aliens, just as in the very first adventure where the space jellyfish basically shouts at her so loud she nearly goes crazy with emotion. Cases like "The Bonding" and "Survivors" are in that category, too. Although they all are also in the category of "a distance of a few hundred kilometers"... Timo Saloniemi
In the Bonding she sensed normal humans though, even if it probably was a strong emotion (the lady's anguish in the moment of dying/being fatally wounded)
The presence she sensed later on was inhuman. Would the initial wave of whatever, after Riker cuts direct communications, really be something that emanates from the landing party? Or already the local spirits reacting to the death in the landing party? Timo Saloniemi
For Troi to even exist is a miracle. I mean we all know her mother's disposition, so how could she tolerate a Human male? Think about it, if her father even glanced at another woman and for only a split second thought, "I'd do that"...
...Then what? Lwaxana is the ultimate voyeur anyway. I don't know if Betazed has maize, but I'm sure there's a local delicacy comparable to popcorn. Timo Saloniemi
It has been suggested that when Deanna "read" the emotions or intentions of somebody on the viewscreen, it wasn't actually via telepathy, but it was her 'empathic' ability giving her much higher sensitivity to that person's body language, verbal and facial cues, etc. This would (retroactively) make sense in the case of Ferengi in "The Battle," since it was later revealed that Betazoids can't read Ferengi minds. Kor
Yes, but we do get an indication: TROI: How can you know that? Tam? You're in contact with it. With Tin Man. Aren't you? TAM: No. Well, yes, a little. But not quite on a conscious level. TROI: We're light years away. That's impossible, even for you. TAM: Impossible for me. Maybe not impossible for Tin Man. So, Tin Man was able to initiate an unconcious telepathic contact with Tam from lightyears away (though its not said how many). The conversation would suggest that Tam's telepathic capabilities could be in the range of 1 lightyear (within 10 trillion km - but it could be anywhere in that range). 1 Lightyear is approximately 50 000 AU... but I'd imagine that would be an exteme maximum for Tam (probably subconcious level, if not impossible). I'd give tam maybe 0.25 to half a lightyear of maximum range. Considering ships in Trek are supposed to be able to engage in combat at hundreds of thousands of km from each other and Troi was usually detecting people's emotions from across the screen when ships were in those ranges, I would imagine that her's empathic abilities could have a range of about 500 000 to 1 million km (maybe a few million km). A Betazoid such as Lwaxana Troi (and a full blown telepath) may have telepathic range that reaches across 1 AU or slightly more (149.6 million km). And someone like Tam could be anywhere from solar system range to 12,500 AU. Though, we've seen that in Star Trek Enterprise, T'Pol and Tucker were linked together across lightyears... but T'Pol is Vulcan... and its possible their telepathic abilities are more powerful than Betazoids and work across lightyears instead?
Vulcan telepathy does work across some distance, depending on degree, intensity, mental power, or whatever. In "The Immunity Syndrome," Spock sensed the death of all 400 of the USS Intrepid's Vulcan crew happening way out in another star system... as if millions of voices suddenly cried out in terror and were suddenly silenced. Oops, wrong franchise. And in TMP, he felt V'Ger's 'consciousness calling to him from space.' Kor
Or then the conversation suggests that Elbrun can do telepathy across five hundred meters. After all, that's what it takes to cover the entire ship, which is the only feat Elbrun is known to be capable of at that point. Talking with Tin Man is something everybody agrees he is incapable of, and the ability to read the Romulan commander surprises our heroes when it happens later on. Nothing as such establishes that Elbrun would be capable of greater-range contact than other Betazoids, half-Betazoids or fellow Betazoid prodigies. Or of shorter-range only. But it's possible to read the "even you" part of the dialogue as suggesting range-related knowledge hidden from the audience. And might be conceptually different altogether. Telepaths in Trek are sometimes compatible across species borders, sometimes not. Might be techniques as diverse as telephoning, semaphoring and drumming are involved. Or then the differences are as minor as between telephoning, faxing and emailing. Or then it's merely a case of different species using different flag colors for their semaphoring. Can Vulcans read minds, as in, communicate with coherent messages akin to speech? Yes, when in physical touch with their target. Not if he is across the room. But yes again if an intimate bond exists through katra sharing. Perhaps injecting some katra through one's fingertips is the one necessary step, after which range becomes irrelevant and arguably infinite? Betazoid contact clearly doesn't work quite that way... Being able to read the mere image of the Ferengi sounds likely. But Elbrun thinks it a big deal that he can read nothing out of Data. Is he just personally amused by this bit of trivia, or should all Betazoid experts inform their employers whenever their target isn't actually radiating mental telltales and the expert is relying purely on imagery? Troi never gives Picard such a warning. Timo Saloniemi