The Orbitoscope, a six-axis macro-imaging robot for photogrammetric 3D-digitization of insects and other small specimens

Natural history collections contain vast numbers of small, fragile specimens whose morphology is difficult to capture using conventional 2D-imaging. Photogrammetric 3D-reconstruction from multi-view photographs can preserve surface colour and enable scaled measurement, but at macro magnification it typically requires dense viewpoint coverage with high overlap and extended depth-of-field (EDOF) imagery. Existing robotic systems often achieve viewpoint variation by rotating and tilting the specimen, which can be limiting for elongated, heavy, or fragile mounts and for objects whose geometry may change when reoriented. We present the Orbitoscope, an open-source six-axis macro-imaging robot that keeps the specimen stationary while moving the camera in translation (X-Y-Z) and orientation (A-B) around it, with a dedicated stacking axis (C) to acquire focus stacks automatically. We demonstrate the workflow by digitizing six insect specimens and generating scaled, textured 3D models suitable for preservation, measurement, and online dissemination. Basic measurement validation on one specimen showed a mean absolute percent error of 0.52% (max. 0.88%) relative to calibrated microscope reference measurements. Hardware, software, and documentation are openly released, with detailed build and operation instructions archived separately as a technical package.