Comment 13 for bug 1263852

If you are able to compile Stellarium from source and you have a Launchpad
account, getting the newest version of the translations is easy.

You can request a translation download from that language's overview page,
as described here:
https://help.launchpad.net/Translations/YourProject/Exports#Requesting_a_one-off_download

For Stellarium, the links for Chinese (Hong Kong) are:
https://translations.launchpad.net/stellarium/trunk/+pots/stellarium/zh_HK/+export
https://translations.launchpad.net/stellarium/trunk/+pots/stellarium-skycultures/zh_HK/+export

Some time after you request translations download(s), you'll get e-mail(s)
with links to download them. The files will be archived (zipped).

You need to unarchive them, and then put them in the appropriate
sub-directories of the po/ directory in Stellarium's project folder. You
will also need to rename the files. The move and rename should look
something like this:
stellarium.po -> po/stellarium/zh_HK.po
stellarium-skycultures.po -> po/stellarium-skycultures/zh_HK.po

Then you'll need to rebuild Stellarium to re-compile the language files.