Stellarium install instruction:

Download Zip from Github:

https://github.com/siddhariyalskycultures/stellarium-skycultures/tree/sidhariyal

Unzip folder:

Copy siddhar_iyal folder:

Paste siddhar_iyal folder in C:\Program Files\Stellarium\skycultures:

Open Stellarium on desktop and select Sky and viewing options window.

Change settings and sidhariyal tamil will be updated.