CHAPTER V - OTHER ASTRONOMICAL INSTRUMENTS

Summary

Of the other instruments used for astronomical purposes the following are the chief:—

1. The Altazimuth.

2. The Mural Circle.

3. Borda's Repeating Circle.

4. The Zenith Sector.

5. The Reflex Zenith Tube.

6. The Sextant.

7. The Box Sextant.

8. Troughton's Reflecting Circle.

9. The Dip Sector.

10. The Floating Collimator.

11. The Orbit Sweeper.

The instruments comprised in the above list are, for the most part, not required for the purposes of the amateur astronomer. We shall therefore content ourselves with a very brief mention of each, adding, however, references for the use of those who may desire to know more about them.

The Altazimuth, as its name implies, is for the measurement of altitudes and azimuths. It may be considered as a modification of the ordinary transit instrument, the telescope, circle, and stand of which are capable of motion round a vertical pivot. The altazimuth may therefore be used for meridional or extrameridional observations indifferently, and when of a portable size, may be looked upon as a theodolite of a superior construction.

The Mural Circle consists of a graduated circle furnished with a suitable telescope, and very firmly affixed to a wall (murus) in the plane of the meridian. It is used for determining, with great accuracy, meridian altitudes and zenith distances, from which may be found declinations and polar distances.