p7000 astrophotography focus problem

hi there I am new to the site but am very interested in all of the knowledge out there , a camera I want to take on holiday to texas this year is my Coolpix p7000 but when so far I have taken test shots of the night sky / stars it will not focus , not matter what I try , manual / infinity anything
I must be doing something wrong but not sure what any ideas , I don't want to take my d200 as this is all so much bigger to take
look forward to any help
thanks all

tony