Allen D Well the body of the text is getting untidy so -- a new piece of paper. At this time we have agreed that so long as an object on the line of the axis of rotation of the Earth (or the stars) appears in the frame of the camera, then that point will be the centre of circular star trails recorded providing only that the camera has a fixed relationship with the Earth. As Neville J puts it - We attach the camera to the ground we stand on and we leave it alone for the period in question. If, when we develop the film, there is rotation of the stars about an axis, then either the World has rotated and the stars are stationary (HC), or the stars have rotated in the opposite direction whilst the World is stationary (GC). But here is the sticking point (from the last post) - It gets more difficult to visualise the other part. No it is not. It is the exact same action, with the exact same stars, only a larger motion ..What is difficult to visualise is the fact that we don't see it, when we see the other for the same reasons, and yet you insist that it exist.......I do not concede this point yet as there is a fundamental difference. no differenece same action (rotaion about an axis) same stars, same camera... concede?..its a indisputiable fact, if you wish to deny that, you can but that will allways be the reason you cant fully appreciate the problem In your comments above, I can perceive only one axis of rotation -- about the Earth Geographic Polar Axis which when extended becomes the Celestial Polar Axis. I have admitted that this is the determining factor in the focus of star trails obtained from a stationary camera nailed to the Earth. All this is summed up in Philip M's words - ... All of the stars as observed on earth rotate around the celestial axis for no other reason than that the world turns. If GC is spot on then the stars rotate around this celestial earth axis. If HC is spot on, then no stars rotate anywhere, and certainly not around the ecliptic.... [Emphasis added]. Further down he alludes to changing the Earth's axis of rotation. At this time, I pose the question, what would be the effect of changing the Earth's attitude so as to bring its axis of rotation -- its Geographical Polar Axis -- into alignment with the Ecliptic Polar Axis? I suggest that, in the heliocentric scenario, the effect would be to make the NCP the new focus of nightly star trails, all other conditions previously agreed remaining true. In the geocentric scenario, the universe's axis of rotation would have to be changed at the same time. I'll pause here till you respond on this question. Paul D National Bingo Night. Play along for the chance to win $10,000 every week. Download your gamecard now at Yahoo!7 TV. http://au.blogs.yahoo.com/national-bingo-night/