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1. Halley's 5-foot transit instrument.
	The earliest telescope at the Royal Observatory Greenwich that can definitely be associated with its history is Edmond Halley's (1656-1742) 5-foot...

2. Quadrant, c. 1768.
	A brass quadrant, made in London by John Bird c. 1768.

3. Reflecting circle - Borda type, c. 1790.
	A reflecting circle was used to measure the distance between the moon and certain stars in the 'lunar distance' method of finding longtitude. Trade...

4. Bradley's 8-foot brass mural quadrant.
	Bradley's quadrant follows the same design as Halley's, the main difference being the metal used. After twenty years of use, the frame of Halley's...

5. A sextant.
	The sextant was first made in the late 1850s by the London instrument maker John Bird, then one of the finest makers in the city. He was commissioned...

6. A compass, 1766.
	The first major improvement to the mariner's compass came in the mid-18th century with the work of Dr Gowin Knight. In 1745 he invented a method of...

7. A cross-staff, c. 1700.
	The cross-staff was a device for measuring the altitude of the sun or Pole Star. It made use of the properties of right-angled triangles, or...

8. A double sextant, 1797.
	The sextant takes its name from its shape, a sixth of a circle. Astronomical sextants had been in use since the 16th century but the marine version...

9. A back-staff, 1755.
	A back-staff is a navigational instrument that was developed in the 1500s to measure the height of the sun above the horizon, and so determine the...


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