Originally posted by bdery: I did calibrate once. I was looking due south.
How did you set that up? Compass?
Originally posted by bdery: I read that wider lenses are not ideal.
That is what I have read too.
Originally posted by bdery: What bothers me, however, is that both crops look the same, whether astrotracer is active or not. Especially the foreground. Whatever else happens, the trees should be blurred if astrotracer moves the sensor, shouldn't it?
Yes, the astrotracer works by moving the sensor, very slowly, to account for the rotation of the Earth.
If the foreground is not blurred then I would suspect the function of the astrotracer either was not set up and active during the shot, or it has malfunctioned somehow.
But how much foreground blur should be dependent on the focal length and how long the exposure is.
I made some night shots with my K5IIs and a Sigma 28mm manual lens last year in Death Valley, and was able to get great shots without an astrotracer. I set the camera up to expose for about 30 seconds, and was able to get pictures without star movement.