Today is Ahoi Ashtami in northern India in which women keep fasts for their children's well-being just like they do for their husbands on Karva-chauth. While they break the fast on Karva-chauth after seeing the moon on Ahoi or 'Hoi' as it is locally called they break the fast after seeing the evening star.
The detailed stories and rituals can be read in this Drikpanchang page but I am more concerned with the identification of the Goddess Ahoi. She seems to be similar to Goddess Shashthi in the sense that she is worshipped for keeping children healthy but the latter is associated with the 6th day not 8th and am not sure if they are the same.
So my question is - Do any scriptures mention the story or give clues to the identity of Goddess Ahoi who is worshiped on Ahoi Ashtami?