In the Argelius Sector we find one of the oddities of The Original Series…a system referred to by its Bayer designation and ancient name in the episode “Who Mourns for Adonais?“ This would be the Pollux, or Beta Geminorum system located at 31,-15.
Also in this quadrant, and depicted on the STO Sector Map, is the titular system of the Sector: Argelius. Argelius II features in the TOS Episode “Wolf in the Fold,” where Scotty is accused of murder and Kirk has to deal with the “Status of Forces Agreement” the Federation has with the Argelians…and we find out Jack the Ripper is an alien entity. ST:Star Charts places Argelius as Iota Leonis, but again this just cannot be since cannot be reconciled with “real” (our purpose here) and distance…Iota Leonis is 79 LY away and located 69,38 which would place it at the north end of Romulan space towards Gamma Hydrae. HR3259, G-class star, is located in the appropriate spot, so reconciling that star as the Argelian star seemed the right thing to do. (There is an obscure reference to an “A” and “B” star in the Argelian system, and that Argelius circles the “B” star…I’d suggest that this is a kind of notation indicating the three stars of an Argelian inhabited “cluster” composed of A = GL309, B= HR3259, C= LHS 246.)
Associated with the “Wolf in the Fold” episode, a mention was made of “one of the first established human colonies” at Alpha Proxima (sometimes Alpha Eridani, Alpha Eradoni.) Needless to say that Alpha Eridani (Achernar) is out of consideration since its distance is negated by ST:ENT canon’s mention of 90 light years and Alpha Eridani is 139 LY. There are no human Eradoni or Proxima constellations, but I would suggest that Eradoni could have been an Andorian designation that was phonetically similar to Eridani. So Alpha Eradoni and Alpha Proxima could both be accurate, the former as an Andorian designation similar to our constellation system, and when humans adopted some Andorian maps they carried over some designations…which was then superseded/augmented by Alpha Proxima when the human colony was established…the colony being one of the first and closest (Alpha & Proxima.)
What we do know is that this colony was on a fairly direct line between Sol and Argelius, Struve 1321 and LHS 261 are both good candidates for that, being K-class Orange stars there is a good chance of habitable worlds. But 261 sits right on the Vulcan/Argelius sector border…and that is a mental and literal “half way point” between Sol and Argelius, so it is the best candidate for this Alpha Proxima.
Arkonia was the homeworld of the Arkonians, and the events relating to them during the ENT episode “Dawn” occurred in the nearby Xleen system. Metalas Prime was visited by NX-01 Enterprise sometime around April 1st, 2152; and was mentioned by Trip Tucker in the episode “Dawn” (occurring around October 3rd, 2152) as one of the places he was happy to have visited.
Delta Vega is the location where the events of the TOS episode, “Where No Man Has Gone Before” take place. It is assumed the Galactic Barrier is located “up” (that is towards the map viewer) from Delta Vega.
The last matter of non-STO map location is Efrosia, or Efros Delta. This is the home of the Efrosians and is in this approximate area on ST:Star Charts.