A lot of images on Paheal tagged Astrohamus are signed RH in the corner.
RH is also what is displayed on the Pixiv they originate in.
It appears that RH is the new moniker of artist who used to go by Astrohamus and someone recognized their art style.
It's not really clear what RH stands for and might cause confusion if other artists use those initials.
At least one other does on Paheal but they don't draw loli.