PROBLEM 3. The cone being adjusted, and any star proposed, to find its place in the heavens.
The cone remaining at rest, turn the declination segment K till the scale L cuts the proposed star on the projection; note its declination on the scale and set the index M to the same degree on the segment K, when the index will point to the star, which, if the adjustments have all been correctly made, will be seen through the sights P, O.
Example.—To find the star Aldebaran; look for Aldebaran on the projection, bring the scale L to cut it, and you will find it against 16° north declination. Set index M to 16° N. P., and look along the edge of it, or through the holes P, O, and you will see the star.
PROBLEM 4. Having observed a star in the heavens, to find it on the projection.
Set the cone as accurately as you can to the day and hour, then turn the declination segment round, and elevate the index till you can see the star through the sights P, O. Note the declination at the segment K, cut by the index M, and against the corresponding degree of the scale you will find the star on the projection.
If no such star can be found, you may then conclude that it is a planet, or a new star.
By this means the place of the moon, of a planet, or a comet, may be noted down, from time to time, and their apparent paths traced out. [p377]
PROBLEM 5. To find the hour of the day by the sun.
Turn the segment K, and elevate the index M, till the sun is seen or shines through the sights O, P, and the scale L point to the hour and minute on the circle E F G.