It's worth bearing in mind that one of the primary source documents for the SFU is the
Star Fleet Technical Manual, though the scale of the galaxy itself is somewhat different in the SFU than it is in the SFTM.
The
Federation and Empire hex map is 61 hexes across and 19 hexes down; each
F&E hex is 500 parsecs across. (Thus, the galactic disc is only one hex thick along the z-axis.) The Federation is at the centre of the
F&E map; ever since the Border Declaration of Y102, it has claimed a disc 9500 parsecs (or 19 hexes) in diameter. The founding member planets (such as Earth, Vulcan, and Andor) are located in
F&E hex 2908 (the UFP's "capital" hex); the Orion home world is in
F&E hex 2812.
Rather than having four quadrants, the SFU Milky Way
is divided into 24 sectors, grouped into five regions capable of hosting life as we know it. The Alpha Octant extends across the Alpha, Beta, Gamma, and Delta sectors; the
F&E hex map covers the outermost two-thirds of the habitable zone of Alpha, Beta, and Gamma. Immense Voids in the Epsilon and Omega sectors divide the Alpha Octant from the Sargasso Storm Zone and the Omega Octant respectively, while the "off-map" area coreward of the
F&E map eventually runs into the Storm Zone (not to be confused with the Sargasso Storm Zone), a region surrounding the galactic core which cannot sustain long-term occupation.
Of the five habitable regions of the Milky Way, only the Alpha and Omega octants have thus far been explored in print. Neither Sargasso nor the distant Sigma Octant (the next octant over past Omega from Alpha) have been written about much as of yet, though the Xorkaelian Tyranny - which holds the largest habitable region, over on the opposite side of the galaxy from the Alpha Octant - is set to become the "big bad" of the
Module X2 era.
That said, there is material in the SFU looking at a number of places outside of the Milky Way, or at least for certain extra-galactic factions. The Tholians and Seltorians are from the M81 Galaxy; an enclave of Tholians would later appear in the Draco Dwarf galaxy, while some info has been printed regarding the main "pirate" faction back in M81. The Bolosco and Zosmans (a pair of rival Omega factions) are each from beyond the Milky Way, while the Iridani (also encountered in Omega) are based in a nearby extra-galactic cluster. There is a published module looking at the Lesser Magellanic Cloud and a playtest file exploring the Triangulum Galaxy. As the name suggests, the Andromedan Invaders hail originally from the M31 Galaxy. While the Juggernauts are also from some other galaxy, though no-one is quite sure which one...