The latter will feed a guide-eyepiece and two guest-eyepieces simultaneously and is served by an access-platform large enough to accommodate several observers, integrated in the telescope mounting itself: it was these design features which dictated the choice of altazimuth mounting
With a telescope that rides on an altazimuth mounting
, such as a Dobsonian, no effort will be required to maintain this orientation, but with an equatorially mounted instrument it will be necessary to adjust the alignment of the eyepiece periodically.
The majority of today's big-aperture telescopes (professional as well as amateur) use an altazimuth mounting
With the excitement of the eclipse now ended Ainslie returned to matters of telescopes and instruments and eight months after the eclipse, at the 1928 March 28 meeting, (54) Mr Sellers read his paper entitled 'A portable Altazimuth mounting
', which of course was of great interest to Ainslie.
Picking out the planet in the predawn sky, his first views were "so much affected by the waves of vapor passing along the horizon as to be constantly flaring and molding in a manner which scarcely enabled the phase to be made out." But by laboriously turning the manual slow-motion controls of his telescope's altazimuth mounting
, he was able to follow the planet as it rose into the brightening twilight.