Altitude scale and azimuth circle on CAA's (Cambridge Astronomical Association's) half-metre Dobsonian. The black box holds rechargeable penlite cells which power red LEDs to illuminate the scales.

Close-up of the altitude scale on the CAA half-metre Dobsonian This scale is paper (printed from the program you can download from this site) stuck to the plastic bearing tube with PVA glue.

Close-up of the azimuth setting circle on the CAA half-metre Dobsonian. This setting circle was made from 3mm thickness plywood.

On this scope the altitude bearing was of a small diameter, so a large circular altitude circle was fitted (rather than the usual linear scale fitted to the inside of the bearing tube). Both circles were cut from 2mm MDF and given a few coats of quick-drying water-based primer and water-based gloss paint.

The same telescope was later adapted to allow left-hand or right-hand use, and the Psion computer was mounted on a removable platform.

Close up of the Psion computer on its removable platform.