You will get all achievements except archivarius through basic gameplay. To get three stars on all constellations will you have to play all constellations three times. My tip for doing this is playing the same constellation 3 times in a row to begin with instead of discovering all constelattions. that way is it easier to know what you are done with or not. you can see how many stars you have on the current constallation in the top right corner.

Discoverer
Discover first constellation



True North
Discover Polaris in the Little Bear



Two Bears High Fiving
Find the two bears shining brightly in the sky



Stargazer
Discover all constellations



Archivarius
Get three stars on all constellations

Hope this guide helped, there isn't that much to cover about this game and its achievements since its fairly straight forward but i thought i'll make this guide anyway if anyone had trouble and just for the fun of it :D.

Have a nice day.