Stellarium

It looks like it's not currently available in the store - I can't find it in the US or UK app stores either, it wasn't developed by the Stellarium team (http://www.stellarium.org), and I can't find a website for the developer so I don't know if it's gone from the store permanently or not. Are there other similar apps in the store that are of any use ?

The Stellariium app used to be available in the US store (and possibly in the Italian store as well), but I don't think that it's in there now. Unfortunately I haven't been able to find the developer's site, so I don't know whether it's only gone temporarily or for good.

I haven't used any planetarium or constellation apps so I can't recommend any - you could do a search for 'planetarium' in the Italian app store and then have a read through the app's descriptions and reviews/ratings to see if any do what you need. Or has you friend got any other similar apps that he uses that he could recommend ?