All of these guys are correct. Leroy Guatney also has an update/errata/Corrections of Book 6 scouts on the web somewhere, or did, as of a year ago, at least. Mostly corrections of some interpolation errors and such in the stellar charts. But if your players are not hard core astronomers or physicists, they really won't notice any glaring errors if you use the book as is.
Digest Group did Grand Survey (worlds) and Grand Census (societies). I have both, and they smoke, though Grand Survey is much more useful, overall for the type of stuf that I do with science fiction writing in general. Either can be sometimes had on eBay, ranging from 21.00 to about 40.00 if the bidding gets hot.
Grand Survey is pretty much my world building bible. Some excerpts of that material are mirrored in very old issues of JTAS. Special Supplement: Atmospheres comes to mind.
Gurps Space 4th ed is pretty good, as is (in a generic way) Decipher's Star Trek plug-in "Worlds" from drivethrurpg.com. Hero Games star hero is pretty good, too.
Later, DGP re-released a lot of that material as World Builder's Handbook.
GDW (I am not sure how the licensing went on this one) also put out "World Tamer's Handbook", which in my opinion was not up to par, really.