On Sun, Oct 16, 2011 at 05:20:25PM -0700, Larry Colen wrote: > > On Oct 16, 2011, at 9:22 AM, Matthew Hunt wrote: > > > On Sun, Oct 16, 2011 at 12:06 PM, Larry Colen <[email protected]> wrote: > > > >> I read something about the astrotracer not working perfectly with > >> rectilinear wide angles because the stars at the edges leave traces. > > > > Are you sure that this issue has to do with rectilinear lenses, > > specifically? > > No I'm not sure, something of that sort was mentioned in that "night > photography" photo book that was just posted. > > > > > What comes to my mind is this: The correct movement to track the sky > > is rotation about the celestial pole. The astrotracer tries to > > approximate this motion using the sensor movements available to it: > > rotation about the sensor center, plus translation. I think that for > > wide fields of view, unless the sensor is centered on the pole, the > > tracking motion is going to be wrong at the edges, no matter what the > > geometric projection of the lens is (rectilinear or fisheye). > > That may well be possible, They need different tracking at different parts of > the sensor. > > Even so, the question remains, in general, are you better off with a > rectilinear super wide, or doing the correction in software?
No, that's not the right question. Rectilinear or fisheye (or anything else) is irrelevant. The necessary correction is a rotation around the celestial axis. If the camera isn't pointed in that direction, no motion of the sensor (basically constrained to be in a plane perpendicular to the axis of the lens) can produce the required image. Whether you want a fisheye, a rectilinear, or any other field of view has nothing to do with it - that's an independent choice. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
