| By far the most popular type is the planispheric astrolabe, on which the celestial sphere is projected onto the plane of the equator. |
| The construction of astronomical instruments such as the astrolabe was also a speciality of the Arabs. |
| Another early navigational instrument that relied on the same principles as the quadrant was the mariner's astrolabe. |
| Unlike the delicate quadrant, the mariner's astrolabe was a thick, weighty instrument typically made of cast bronze or brass. |
| He also wrote works on astronomical instruments, for example on constructing and using an astrolabe. |
| When the ten minutes are up, as signified by the ding of an egg timer, a piece of nautical equipment as pedigreed as an astrolabe or a sextant. |
