I made more experiments with the compass... Outside (on the balcony) it's not that bad. But inside (in front of the balcony) the needles points towards my main door... I tried to cover up locks, clothes racks etc. but the needle still points in that direction.
Well, I guess if I can use it outside it should be enough, although the compass didn't seem to be perfect. Maybe 90%. As I said, I could buy something to cover up the balcony railing.
Like you, Sil, I would be happy enough to get some help with it. It doesn't have to be perfect...
Still waiting for Celestron to answer...