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Author: Theaker, Robert.
Title: A light to the longitude, or, The use of an instrument called the seaman's director speedily resolving all astronomical cases and questions concerning the sun, moon, and stars : with several propositions whereby sea-men may find at what meridian and longitude they are at in all parts of the world : published for the advance of navigation / by Robert Theaker.
Publication Info: Ann Arbor, Michigan: University of Michigan, Digital Library Production Service
2012 November (TCP phase 2)
Availability:

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Print source: A light to the longitude, or, The use of an instrument called the seaman's director speedily resolving all astronomical cases and questions concerning the sun, moon, and stars : with several propositions whereby sea-men may find at what meridian and longitude they are at in all parts of the world : published for the advance of navigation / by Robert Theaker.
Theaker, Robert.

London: Printed by William Godbid for William Fisher ..., 1665.
Notes:
"Licensed, June 28, 1665. Roger L'Estrange"
The table of contents and the epistle ([4] p.) are bound and photographed between pages 30 and 31.
Errata: p. 32.
Reproduction of original in Bodleian Library.
Subject terms:
Navigation -- Early works to 1800.
URL: http://name.umdl.umich.edu/A64474.0001.001

Contents
title page
The CONTENTS.
To the KING's most excellent Majesty.
To the READER.
part
The full Description of an Instrument lately In∣vented by Robert Theaker, but now upon his request explained, and the manifold Ʋses thereof written for the general good, by Charles Saltonstal, Professor and Practitioner of the Mathematick, neer the Postern-gate on East-Tower-hill.
The Description of the Ʋpper Moving-Sphere or Plain, representing the Celestial Globe.
Having the day of the Month known. To find the Sun's Declination, his place Sign, and Degree in the Ecliptick, and his right Ascension in Degrees and Minutes or in Hours and Minutes.
The Sun's place in the Ecliptick being known, to find the Hour and Minute of the Sun's Rising or Setting any day of the Year.
To find any fixed Stars Declination, right Ascension in Degrees and Minutes, or in Hours and Minutes, his place, Sign, and Degree, or Longitude in the Ecliptick, and day of the Month belonging to that Star.
To find, every day in the Year, when any of the fixed Stars comes to the South.
To find, every day in the Year, when any of the fixed Stars Riseth or Setteth.
To find the Sun's Rising or Setting the same way as you find the Stars Rising or Setting.
To find the Sun's Altitude every day of the year when he comes to the Meridian.
To find every day how many Degrees the Sun or Stars dip∣peth or goeth under the Horizon at Midnight; Also to find the Amplitude of the Sun or Stars every day in the year at their Rising or Setting.
To find at all Altines when the North Star is directly South above the Pole, or North under the Pole.
To Draw the Parallels of the Sun or Stars Declinations, and thereby to know when they Rise or Set, or whether they Rise or Set at all.
To find, every Day in the year, at what time any of the Planets cometh to the South.
To find the true Distance of the Moon's Motion from the Sun.
To find the longitude, by knowing when any of the fixed Stars cometh to the South.
To find exactly the True Meridian and Longitude of the City of London.
Example. The first of April, I demand how the proper and particular Meridian and Longitude of the City of London may be found and discovered, by this Instrument.
To find the true Longitude of the City of London, at the Sun's Setting. Example.
THE THIRD WAY. To find the true Longitude of the City of London: at the Sun's Rising.
THE FOƲRTH WAY. To find the true Longitude of the City of London by the Moon when she cometh to the South.
ANOTHER WAY. To find the true Longitude of the City of London by the Moon when she cometh to the South.
Two several Questions by finding the Moon South to know what Meridian you are at.
The first Question.
Example.
The second Man having the Moon South at 6 hours 29 minuts.
The third Man having the Moon South at 6 hours 32 minutes.
The Second Question.
Example.
The Rule and reason for turning the upper Shere is from 360 degrees.
To cut the Horizons for all Latituds.
Errata.