Canon g12 how to keep manual focus in time lapse to avoid focussing on raindrops

[canonnewbie111]

Hi. I hope you'll forgive me if I use the wrong vocabulary but I'm new to photography I am using a canon g12 to take landscape time lapse photos using an external plug in 'timer remote' (that fires every 20 seconds)My problem is raindrops on the window - they cause the camera to focus on the window and not the landscape..Ive tried setting the focus manually but it seems every time the timer 'fires' the focus is reset to 'auto'I'd be ever so grateful if anyone could please give me any pointers? Thanks ever so much for any help you can offer. Thank you!