From tripod to tracker: the first real exposure

This is the session where the ideas become mechanical, and the order matters because each step depends on the last.

Balance the camera before anything else

A ball head holding a camera and lens cantilevered sideways is where most sag happens. A head rated for the camera in daylight is not necessarily rated for it held out for four minutes, and any droop shows as trailed stars.

Polar align better than feels necessary

Exposure length is set by alignment quality and focal length together. Spend the extra five minutes here rather than discarding half the frames later.

Focus on a bright star, not on infinity

Lens infinity marks are not reliable, and focus shifts as the lens cools. Use live view at maximum zoom on a bright star, or a diffraction mask if you have one, and check it again partway through.

Take a test exposure and look at the corners

Round stars in the centre and trailed stars at the edge mean the lens rather than the tracking. Trailed everywhere in the same direction means tracking or alignment. The corners are the diagnostic.

Then take far more frames than you think you need

And take dark frames at the end, with the lens capped, at the same settings and temperature. That is what makes the stack clean, and it costs nothing but time you are already spending outside.