Hi, I have been shooting time lapse videos for a while and i want to upgrade to motion timelapse but i have no idea which Slider or control module i need. I have a horribly low budget so a DIY would be great but anything under 400 would be affordable. I like to photograph stars using long exposures so i would need a step system so no movement occurs in my 30 second exposures right? Any help would be welcomed! Thanks.