Portable telescopes are commonly small, ranging from about 2½ inches to about 5 inches in aperture. The former is the smallest that can fairly be considered for celestial observations. If thoroughly good and well mounted even this is capable of real usefulness, while the five inch telescope if built and equipped in the usual way, is quite the heaviest that can be rated as portable, and deserves a fixed mount. Setting up an alt-azimuth is the simplest possible matter. If on a regular tripod it is merely taken out and the tripod roughly levelled so that the axis in azimuth is approximately vertical. Now and then one sets it deliberately askew so that it may be possible to pass quickly between two objects at somewhat different altitudes by swinging on the azimuth axis. If one is dealing with a table tripod like Fig. 69 it should merely be set on any level and solid support that may be at hand, the main thing being to get it placed so that one may look through it conveniently. This is a grave problem in the case of all small refractors, which present their oculars in every sort of unreachable and uncomfortable position. Of course a diagonal eyepiece promises a way out of the difficulty, but with small apertures one hesitates to lose the light, and often something of definition, and the observer must pretty nearly stand on his head to use the finder. With well adjusted circles, such are commonly found on a fixed mount, location of objects is easy. On a portable set-up perhaps the easiest remedy is a pair of well aligned coarse sights near the objective end of the tube and therefore within reach when it is pointed zenith-ward. The writer has found a low, armless, cheap splint rocker, such as is sold for piazza use, invaluable under these painful circumstances, and can cordially recommend it. Even better is an observing box and a flat cushion. The box is merely a coverless affair of any smooth ⅞ inch stuff firmly nailed or screwed together, and of three unequal dimensions, giving three available heights on which to sit or stand. The dimensions originally suggested by Chambers (_Handbook of Astronomy_, II, 215) were 21 × 12 × 15 inches, but the writer finds 18 × 10 × 14 inches a better combination. The fact is that the ordinary stock telescope tripod is rather too high for sitting, and too low for standing, comfortably. A somewhat stubby tripod is advantageous both in point of steadiness and in accessibility of the eyepiece when one is observing within 30° of the zenith, where the seeing is at its best; and a sitting position gives a much greater range of convenient upward vision than a standing one. When an equatorial mount is in use one faces the question of adjustment in its broadest aspect. Again two totally different situations arise in using the telescope. First is the ordinary course of visual observation for all general purposes, in which no precise measurements of position or dimensions are involved.