I’m afraid we currently don’t support animated GIFs. I think if you try to upload one, you will only see the first frame of the animation.
Technically, this restriction is imposed by the Drupal content management system we use. Its image processing modules don’t support animated GIFs.
From memory, with a bit of hackery we could work around those restrictions. I understand that for applications like showing transient objects like variable stars, and the rotation of planets, they’re really useful. However last time this was discussed it became apparent that animated GIFs are quite polarising and a number of people really don’t like them.
So, as things stand we don’t support this, but we are aware of the feature request.