Allen D Just got your second response. You didn't comment on my illustration! I'm not sure that I follow exactly what you are saying in your last (I'll grapple with it later) but to your earlier post, I have this to say - I see what you're talking about now. You see you confused the issue with talk of the eccentricity of the Earths orbit (and other points) -- and this is doubly irrelevant. However, I take considerable heart from what you have said. Your simplified explanation of the photographer sitting 'on top of the world' pointing his camera up (which will not work in practice -- it's not sufficiently precise) but something along the lines I have proposed would work and for the same reasons you have advanced ie the ratio of a mean solar day to a sidereal day etc. But the point that interests me is this -- if my system were implemented, and it takes circular star trails centred upon the ecliptic pole, then you would have to admit that the Earth does move on an annual orbit of the Sun because if the universe rotates on the geo polar axis (the classic celestial poles) then the trails MUST -- by your assertion -- be elliptical in the ratio of 0.918:1 a difference in axes of about 8% and that should be unambiguosly determinable! Do you stand by this? It's time I went to bed -- the birds are about to start chirping! Paul D Sick of deleting your inbox? Yahoo!7 Mail has free unlimited storage. http://au.docs.yahoo.com/mail/unlimitedstorage.html