dovetail mounts and 'elephant foot' from printing

For sliding dovetail mounts an 'elephant foot' from over extrusion of the first layer will prevent good alignment. This applies to both halves of the dovetail.

Illumination: The illumination_dovetail part does not reach the print bed. The condenser part has a chamfer at the print bed to account for this effect.

Optics dovetail: The z-axis of the main body does not have a chamfer. On the optics modules the dovetail does not reach the print bed. The camera_platform_picamera_2_pilens does not have a chamfer.