If you visit A-Dome memorial you’ll want to visit the Peace Museum. However be prepared for the coach loads of tourists, often on guided tours. You might find this intrudes on what otherwise should be a sombre and reflective occasion. This is a shame particularly if the visit has been one of your principle reasons for coming to this part of Japan. There would seem to be two ways to avoid this. The first would be to be there as soon as the museum opens in the morning. The other, if it fits in with the rest of your schedule/itinerary, is to make two separate visits timed for an hour before the museum closes. (Entrance is only ¥50 yen) There are two floors: visit the lower floor on the first visit, and the upper floor on the second visit. This is what we did in mid November and there was hardly anyone else there. Dusk is also a great time to see the A dome memorial and the Peace Park. But I think you’ll need two visits at this time of day. IMO there’s too much information to absorb in only an hour.