You don't give your zone but in my zone this is a good time to move a peony--be sure you research how to replant the tuber, and also fine to move the asters. They're not at all established yet.

if someone felt it was time to sell you a potted aster .. then one might be able to presume that it is a good time to plant them ... [not always .. but most the time]

replanting something you just planted a few says ago.. should not really add all that much more stress ...

and fall is very forgiving.. with its cool nights .. to overcome whatever heat the day may have brought ... so the default answer is usually yes ... but as noted.. where you are might matter.. big city name ....

what she said about peony ... look for videos in a search engine ...

ken

great time to divide the peony roots if it is old and you want more of this particular variety. do not simply replant it.

Yep, perfect time to transplant the peony -- ground still nice and warm, will help roots get established while top growth slows/stops for the season. If you do it now, it should bloom in the spring.

If you just planted something a few days ago, moving it is not an issue at all -- you put it in a hole, three days isn't enough time for anything to establish.

Yes to Alex. Peonies aren’t transplanted, but healthy root tuber divisions with eyes for growth next year are easily planted. You can throw away the central root portion after division if you want it out if that spot.