Yeah, it'd be nice to have sub-pixel control in Flash, but it's not going to happen in a hurry.
I've had a few jobs like this, whereby the subject matter needs to move slowly and it's because of the leap from pixel to pixel that makes it jerky - for slow-moving items there needs to be a half or quarter step per frame to make it feel more realistic.
I'd suggest making it more dramatic, like a time-lapse sunrise...
Nah, looks fine to me too!