Hi Margaret,
Ive been thinking about your puzzle for a while, im not sure that it refers to anything to do with astronomy... Perhaps "3:30 sharp" refers to the right-angled shape that clock hands form at 3:30 with the hands pointing to the two locations??...(Although im not sure what the locations mean though....yet...

....some sort of code perhaps???)... And maybe the "giant who is not afraid of fire" is in reference to a mythological creature, as opposed to something atsronomical/astrological???
Could you possibly post a link to the site with the puzzles??... I'd like to give some a go...
Davin