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English scientist George Adams created a very similar backstaff at the same time. Adam's version ensured that the distance between the Flamsteed glass and horizon vane was the same as the distance from the vane to the sight vane. [8]
In navigation the instrument is also called a cross-staff and was used to determine angles, for instance the angle between the horizon and Polaris or the sun to determine a vessel's latitude, or the angle between the top and bottom of an object to determine the distance to said object if its height is known, or the height of the object if its distance is known, or the horizontal angle between ...
Overdrawn at the Memory Bank is a 1984 science-fiction television film starring Raul Julia and Linda Griffiths (pictured).Based on a 1976 short story by John Varley from the Eight Worlds series, the film takes place in a dystopian future where an employee at a conglomerate, played by Julia, gets trapped inside the company's computer, where he is monitored and later abetted by a character ...
Usually made of pear tree or boxwood, with an arch of 15° to 30°, [3] it is an example of a backstaff. This is a drawing of an almucantar staff. There are three vanes - the horizon vane (A), the shadow vane (B) and the sighting vane (C). The sun casts that shadow of a vane (B in the adjacent image) on a horizon vane (A). The horizon vane has ...
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Navigators had been able to work out latitude accurately for centuries by measuring the angle of the Sun or a star above the horizon with an instrument such as a backstaff or quadrant. Longitude was more difficult to measure accurately because it requires precise knowledge of the time difference between points on the surface of the Earth.
The backstaff, which measures the length of a shadow, was used from the 16th century and saw iterative improvements such as the Davis quadrant. These were in use in parallel with the octant and early sextant; the sextant eventually displaced the others, and is still used to this day.
The triangular frame at the top spans 60° as did the arc on the backstaff. The main graduated arc subtends 30° as in the backstaff. The 30° arc is graduated in degrees and sixths of a degree, that is, at ten-minute intervals. The sighting vane of the backstaff is replaced with a sight (called an eye vane [2]) mounted on the end of the index arm.