The dome itself however, is wholly of galvanized iron, in 12 gores joined with standing seams, turned, riveted, and soldered. There is a short shutter at the zenith sliding back upon a frame, while the main shutter is removed from the outside by handles.
Fig. 181.—Detail of Light Metal Dome for Small Observatory.
Observatories of the Romsey or allied types can be erected at very moderate cost, varying considerably from place to place, but running at present say from $200 to $600, and big enough to shelter refractors of 4 to 6 inches aperture. The revolving roofs will range from 9 to 12 feet in diameter. If reflectors are in use, those of about double these apertures can be accommodated since the reflector is ordinarily much the shorter for equal aperture.
The sliding roof, not to say the sliding shelter, forms of housing cost somewhat less, depending on the construction adopted. Going to brick may double the figures quoted, but such solidity is generally quite needless, though it is highly desirable that the cover of a valuable instrument should be fire-proof and not easily broken open. The stealing of objectives and accessories is not unknown, and vandalism is a risk not to be forgotten. But to even the matter up, housing a telescope is rather an easy thing to accomplish, and as a matter of fact for the price of a very modest motor car one can both buy and house an instrument big enough to be of genuine service.
[CHAPTER XI]
SEEING AND MAGNIFICATION
Few things are more generally disappointing than one’s first glimpse of the Heavens through a telescope. The novice is fed up with maps of Mars as a great disc full of intricate markings, and he generally sees a little wriggling ball of light with no more visible detail than an egg. It is almost impossible to believe that, at a fair opposition, Mars under the power of even the smallest astronomical telescope really looks as big as the full moon. Again, one looks at a double star to see not two brilliant little discs resplendent in color, but an indeterminate flicker void of shape and hue.
The fact is, that most of the time over most of the world seeing conditions are bad, so that the telescope does not have a fair chance, and on the whole the bigger the telescope the worse the chance. One famous English astronomer, possessed of a fine refractor that would be reckoned large even now-a-days, averred that he had seen but one first class night in fifteen years past.