Posted by Andrea Tasselli at 17:34 on 2011 May 16
Hello Martin,Well, the problem that I see is if that you use a widefield lens or worse still a semi-fisheye, you’ll introduce certainly some degree of distortions in the field geometrical linearity (those can be of all sorts, barrel, pincushion, cylindrical…). By coarse repositioning the camera each time you’ll run the risk of that the actual position of the sun (assuming it being a near point-like object at that focal length) will be misplaced because of geometrical distortions with respect to the "real" position in the sky (according to the analemma). Now, you might be able to correct it by various software ( I think PS does it) but not really sure whether the reference points you’ll need to have in each shot will be enough to sort this out. Maybe it is nit-picking but better be safe than sorry, as they say! This is worsened (by a lot!) if you intend to use white-light filters, since in that case the correction needed must be extrapolated from other shots as you won’t have any references in each sun shot and I don’t kwow of any program that would allow you to do it (short of doing a lot of heavy mathematics and write the program yourself).Naturally it may be that all this sort of issues are not really of much of significance to you, i.e. you won’t mind if the analemma will come out with a bit of geometrical distortion and maybe some slight offset from the actual position in the sky. I just thought it was worth mentioning…Hope it answers your questions.Andrea T.