The map is based off of one in this book: https://www.amazon.com/Star-Wars-Essential-Daniel-Wallace/dp/0345477642 For the most part the yellow circles refer to ones that have individual descriptions in the book. I made this map to for use in a starwars RPG game I'm running.
Prior to the acquisition by Disney, Star Wars had an official atlas showing the galaxy and where the various planets were. SWTOR had to follow this guide for the planets that were in the atlas.
Now that the atlas isn't canon, when BioWare adds a new planet I'm guessing they just pick an appropriate location.
As a big Star Wars fan, I think a good place to both see if your story is worth pursuing (it most likely is, unless you're ripping off other authors, knowingly or not) and do research on the universe of Star Wars would be The Essential Star Wars Atlas. I have a copy at home and it is a wonderful resource into the history, culture and makeup of the Star Wars universe. I highly recommend checking it out, but if you don't want to spend money, I suggest Wookiepedia.
Nothing wrong in posting your prologue here and getting a few opinions!
The Star Wars Atlas is great for this.
Here you Go!
Here is a link to Imgur, it has the legends sector map I found, a couple different versions of it I made to go ontop of a higher quality galaxy map, some essential atlas maps that have names for the sectors in the expansion region, mid rim, and outer rim, some images from the essential atlas that suggests 1024 moffs and 20 grand moffs, and some potential maps for the oversectors those grand moffs control. https://imgur.com/a/284OMyz
I also found this, an online version of the galaxy map (both canon and legends) which has an option to bring up the sector map overtop of it: http://www.swgalaxymap.com/
Finally, here is a link for buying the Star Wars Essential Atlas, because it is an awesome book and the holidays are coming up, so you should put it on your wishlist:
Well it is a classic though, if you do want good star wars lore about all sorts of crazy planets they have from the Legends timeline I recommend Star Wars: The Essential Atlas I will link it down below on Amazon.
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https://www.amazon.com/Star-Wars-Essential-Daniel-Wallace/dp/0345477642