However, for amateurs' telescopes the more convenient arrangement is the diagonal eye-tube, since it enables the observer to apply any eye-piece he chooses, just as with the simple sliding eye-tube.
[Illustration: _Fig.

7._] We come next to the important question of the _mounting_ of our telescope.
The best known, and, in some respects, the simplest method of mounting a telescope for general observation is that known as the _altitude-and-azimuth_ mounting.

In this method the telescope is pointed towards an object by two motions,--one giving the tube the required _altitude_ (or elevation), the other giving it the required _azimuth_ (or direction as respects the compass points).
For small alt-azimuths the ordinary pillar-and-claw stand is sufficiently steady.

For larger instruments other arrangements are needed, both to give the telescope steadiness, and to supply slow movements in altitude and azimuth.

The student will find no difficulty in understanding the arrangement of sliding-tubes and rack-work commonly adopted.