| At choice two different sighting telescopes with vertical circle are available: The autoreduction telescope of the MEDIA and the standard telescope of the MEJUN alidade. |
| The alidade is a triangular ruler with one or more working scales on it beside other measurements. |
| A variation of the instrument, the marine astrolabe, was designed exclusively for measuring vertical angles to the stars and was limited to an alidade and a circle of degrees. |
| A survey instrument consisting of an alidade, telescope, and vertically and horizontally mounted graduated circles, used to measure vertical and horizontal angles. |
| On the back of the astrolabe, we use the alidade and the two pinholes to point a star. |
| Planispheric astrolabe made of brass and comprising four main pieces: a box or 'mother' made up of five sheets that represent different latitudes, a network or 'spider' with indicators for 24 stars and an alidade. |
