In the Advanced Usage section of the help file, under Importing and Merging, there's a section describing a CSV file format that Astro can import. So you'd have to get the data out of this or any other stellar database and reformat it into the format Astro can import.
Alternatively, you can use the programming language of your choice to insert stellar data into Astro's .AstroDB file since its a standard SQLite file. If you take a look at the tables, they should be very straight forward.
Comments
In the Advanced Usage section of the help file, under Importing and Merging, there's a section describing a CSV file format that Astro can import. So you'd have to get the data out of this or any other stellar database and reformat it into the format Astro can import.
There's a few data sets made this way available on NOX:
https://www.nbos.com/nox/categories/32
Alternatively, you can use the programming language of your choice to insert stellar data into Astro's .AstroDB file since its a standard SQLite file. If you take a look at the tables, they should be very straight forward.