I would assume both of them were feminine.
Petal - I don't dislike it, but it feels too cutesy to be a given name to me. I think it would be a very sweet nickname. I guess it wouldn't be terrible as a full name, I just imagine if it were my name and I think it would annoy me that it was so cartoony-feminine sounding.
Astral - It's not a word, right? But somehow it feels like an adjective. "Oh, how very astral of you". I don't know. Am I just thinking of astrological? Anyway, I can't get past that it sounds like it is describing something. So I'm out for this one.
One momma namenerdin' in the fleeting quiet moments between
delighting in and losing my mind amidst my four kiddos
To peruse my top 100ish names:
http://www.behindthename.com/pnl/82589Bits of blogging here:
http://jodifriesen.blogspot.ca/And family cuteness here:
https://www.flickr.com/gp/41705