2. If the two Stars are of the same altitude, move the globe so that the same degree on the quadrant will cut both Stars, then the index will shew the hour.
This problem is useful when the quantity of the azimuth of the two Stars in the first case, or of their altitude in the latter case, is not known.
If two Stars were given, one on the meridian, and the other in the East or West part of the horizon; to find the Latitude.
Bring that Star which was observed on the meridian, to the meridian of the globe, and keep the globe from turning round its axis; then slide the meridian up or down in the notches, ’till the other Star is brought to the East or West part of the horizon, and that elevation of the Pole will be the Latitude sought.
Prob. XLII. The Latitude, Day of the Month, and the Altitude of any known Star being given; to find the Hour of the Night.
Rectify the globe for the latitude, zenith, and Sun’s place: Turn the globe, and the quadrant of altitude, backward or forward, ’till the center of that Star meets the quadrant in the degree of altitude given; then the index will point the true hour of the night; and also where the quadrant cuts the horizon, will be the azimuth of the Star at that time.
If the Latitude, the Sun’s Altitude, and his Declination (instead of his Place in the Ecliptic) are given; to find the Hour of the Day and Azimuth.
Rectify the globe for the latitude and zenith, and having brought the equinoctial colure to the meridian, set the index to 12 at noon; which being done, turn the globe and the quadrant, until the given declination in the equinoctial colure, cuts the altitude on the quadrant; then the index will shew the Hour of the day, and the quadrant cut the Azimuth in the horizon.
If the Altitude of two Stars on the same Azimuth were given; to find the Latitude of the Place.