no, I did not ask prior to shooting, I paid my entrance fee, went into the museums with my camera, tripod, pano head and other stuff, and did the job. I never had any trouble when doing this. I believe the museum staff did not really know what I was doing. For them I was one of those tourists who, as soon as the bus stops, take photographs of everything around them.
It was always helpful to visit the museums at days when there are not many visitors. And of course it is not possible to arrange for proper lighting, change things in the room etc. if you do the job this way.
In one case I went to the museum reception and asked if they would give me permission to shoot the panos to offer them a virtual tour. They told me that they dont need a tour and that they dont want me to do the photography (probably they did not even know what a "virtual tour" is). I returned a few days later, took my pictures without asking, built a tour and offered it to them. Suddenly they were very interested ...
I must add that in museums in Germany there are normally no restrictions concerning photography as long as you dont use the images commercially. Therefore, when I offer completed tours which were photographed without permission, I tell the potential customer that he may keep the CD for personal use, even if he does not want to buy it, and that I myself will not use the tour commercially as long as I dont have written permission from him.
Holger Schulz, photoaround