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New Colossus of Telescopes

By Paul P. Foster

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In no branch of science is general interest greater, when the popular mind is directed to it, than in astronomy. The idea that we shall at some time find that other planets besides our own are inhabited and that we may eventually communicate with creatures upon those other worlds is always a fertile subject for thought. The hope of making some new step in advance toward this end is deeply stirred al news of such an undertaking as the building of a new telescope, the proportions of which are far greater than any previously constructed.

NE hundred inches or in cities of Pasadena and Los Angeles. The

round numbers, eight feet, observatory was established in 1904 for is the astounding diameter the special purpose of studying the sun, of what will be the great- and the problems of solar and stellar evoest telescope in the world. lution. After a long and careful investi

It will be an American in- gation of possible sites, it was found that strument and is to be erected on the sum- the conditions on Mount Wilson were almit of Mount Wilson, in Southern Cali- most ideal for solar observations, and the fornia, as soon as it can be constructed. directors of the Carnegie Institution have This remarkable telescope has been care- made ample provision for the establishfully planned and

ment and for the funds for its con

maintenance of the struction have been

observatory, durprovided by the

ing at least ten generosity of John

years, the length D. Hooker, of Los

of

"sun-spot Angeles, who, so

period.” far as is known, is

Two unique telethe first man to co

scopes have been operate with Mr.

in constant use at Carnegie in the lat

the observatory ter's efforts for the

since its establishadvancement of

ment. The larger science.

is the Snow teleAs readers of

scope, a reflector, THE TECHNICAL

which has been World may recall,

employed in daily the Solar Observa

observations and tory on Mount Wil

investigations of son is supported by

solar phenomena. the Carnegie Insti

A five-foot reflecttution and is the

ing telescope has newest and loftiest

been completed astronomical ob

and will soon reservatory in the

place the Snow United States. It

telescope, when the is situated on the

Solar Observatory summit of Mount

will be provided Wilson, six thous

with the largest and feet above the

and finest reflector sea, and not far

for solar purposes distant from the JOHN D. HOOKER, Donor of 100-INCH LENS. yet constructed.

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The other important instrument is the Bruce photographic telescope which is designed exclusively for photographing the stars and nebulae. Very wonderful photographs of the stupendous star clouds of the Milky Way have been obtained with this instrument and the exceptionally transparent atmosphere at Mount Wilson makes it possible to photograph some of the best diffused nebulosities, which are obscured by the denser

A BIT OF MOON LANDSCAPE. air at lower levels.

To this observatory has been offered a work progresses and is needed theretelescope which will enable us to pene

for, to be used for the purchase of a trate seven times farther into space than disk of glass one hundred inches in can now be done with the greatest visual diameter, and to meet other expenses telescopes. Its cost will be about one- incident to the construction of a 100twentieth of that of a modern battleship.

inch mirror for a reflecting telescope. The donor's deed of gift is as follows:

In offering this proposal, I make Mr. George E. Hale, Director of no requirements as to the provision

the Solar Observatory, Pasadena. of a mounting and dome for the Dear Mr. Hale:

telescope, but trust to the future I hereby give and place at the dis- that these essential adjuncts will ulposal of the Carnegie Institution the tinately become available. sum of fifty thousand dollars, or so

Very truly yours, much of this amount as may be (Signed) JOHN D. HOOKER. needed, payable on demand as the Los Angeles, Sept. 14, 1906.

The mirror of this telescope will be thirteen inches thick, will weigh four and onehalf tons,

and four years will be required to make the glass and finish the optical work

The glass will be constructed at the great French optical works in St. Gobain, and the difficult operation of figuring, i. e., grinding and polishing, will be under the supervision of Prof. G. W. Ritchey, at the instrument shops

shops in

Pasadena.
THE SUN ECLIPSED BY THE Moon-SHOWING CORONA.

The possibilities of

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upon it.

this greatest instrument of the age are flector, with silvered glass mirror and concisely and comprehensively described with a well-designed mounting, may in the following letter from Prof. Ritchey justly be regarded as the most modern to the donor which was published in the and efficient type of telescope. Los Angeles Evening News, Sept. 15, It should be remembered that a reflect1906:

ing telescope gives superb views of celesSolar Observatory Office, Pasadena, Cal. tial objects visually, also, but it is in pho

July 27, 1906. tography that it is incomparably efficient, Mr. John D. Hooker, Los Angeles. and it is here that results of the greatest Dear Mr. Hooker:

scientific value will be obtained. I have your letter of July 26, in regard First: An eight-foot reflector, which

should have a principal focal length of fortyeight feet, would give revolutionary results in the photography of the nebulae. This is the subject in which I am personally most interested. My photographs of nebulae made at the Yerkes Observatory were obtained with the two-foot reflector, which had a focal length of only ninety-three inches. The eight-foot reflector would have a focal length of forty-eight feet, or 576 inches, that is, six and one-fifth times as great as that of the two-foot reflector; the scale or size of the photographs would be in

same proportion; and with the smooth motion of the telescope

given by mercury flotaFive-Foot MIRROR OF NEW 60-INCH REFLECTOR.

tion, together with the

fine atmospheric definito the field of usefulness of an eight-foot tion and transparency to be had on reflector. The chief uses to which we Mount Wilson, we could certainly expect would put such an instrument are briefly a proportional gain in the minuteness of described below. You will note that all detail and structure shown in these neof these, except the measurement of the bulae. heat of stars, relate to photography. The The great majority of the nebulae are reflecting telescope is especially efficient small and faint—too small for such inin photography, because of its perfect struments as the two-foot reflector at the achromatism and also because of its Yerkes Observatory, or even the Crossgreat speed, since the percentage of light ley reflector at the Lick Observatory. In lost by reflection at the silver film is much fact, there are probably not more than smaller than that lost in passing through forty or fifty nebulae which are sufficientthe lenses of a large refractor. By far ly large for the best results with instruthe most promising lines of advance in ments of the scale of those just named, astronomical investigations are in the di- while the eight foot reflector would give rection of photography; hence a great re- us photographs of tens of thousands of

[graphic]

the

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GREAT STAR CLOUD IN MILKY WAY. Aggregations of stars appear in all parts of the heavens, but this is the most complex and extensive

of all the gatherings of the stars.

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THE MILKY WAY NEAR SAGITTARIUS. A part of the zone-shaped regions surrounding the whole sphere of the heavens, in which stars in

numerable so combine their lustre as to present a milky luminosity.

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