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Forum: Pentax SLR Lens Discussion
09-09-2018, 05:38 AM
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Yes, astrotracer trailing with UWA lenses is an known problem caused by the discrepancy between the spherical coordinate motion of the sky and the central perspective rectilinear coordinate motion of the sensor.
The amount and pattern of trailing depends on the focal length and is very sensitive to the pointing direction of the lens. Pointing the lens toward the celestial equator has worse trailing than pointing it toward either of the celestial poles. Note that if the lens is pointed directly at the pole, you should get no corner trailing at all if the calibration is good.
If I've done my math right, the amount of this kind of trailing is inversely proportional to focal length. So if a 14mm lens has tolerable trailing at 30 seconds, a 28 mm lens will have tolerable trailing at 60 seconds.
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