Yerkes Observatory

“ The world has a right to expect results from such an instrumental equipment, and the Department of Astronomy has in view important researches. Among these are micrometrical measurement of double stars and faint nebulæ; observation of planets, satellites, and comets; photographic and spectroscopic investigation of conditions of the sun; researches on the spectra of fixed stars and nebula?; motion of stars in the line of sight. The Yerkes Observatory will, of course, be used only by advanced students capable of undertaking ”

“ The varying position of the eye end of a telescope, when it is turned to different parts of the sky, makes it necessary to provide comfortable and safe seating accommodation for the observer, more especially when the telescope is a very large one. In the case of the Yerkes telescope, the eye-piece is thirty feet higher when observing near the horizon than when observing near the zenith, and the observer must necessarily follow the telescope. The most convenient arrangement in such a case is to raise or lower the floor of the observatory as occasion demands. ”

“ The largest refracting telescope yet constructed is one of forty inches aperture for the Yerkes Observatory of the University of Chicago. It is interesting to note here that Professor Keeler, in his report as an expert upon the performance of the object-glass, considers that there is “evidence for the first time that we are approaching the limit of size in the construction of great objectives.” Unlike a mirror, a lens can be supported only upon its circumference, and it is the bending by its own weight that proves detrimental to its defining power. ”

“ The largest instruments of this type are the 36-inch Lick telescope and the 40-inch refractor of the Yerkes Observatory.
Fig. 8. Erecting the steel building and revolving dome that cover the Hooker telescope.
Reflecting telescopes, which are particularly adapted for photographic work, though also excellent for visual observations, are very differently constructed. No lens is used. The telescope tube is usually built in skeleton form, open at its upper end, and with a large concave mirror supported at its base. ”

“ From what little causes great events spring! How little can Schwabe have realised, when he began to point his modest little telescope at the sun, and to count the number of spots—the despised spots which he had been assured were of no interest and exhibited no laws, and were generally unprofitable—that he was taking the first step in the invention of the great science of Solar Physics!—a science which is, I am glad to say, occupying at the present moment so much of the attention, not only of the great Yerkes Observatory, but of many other observatories scattered over the globe. ”

“ To the reflecting form of construction belong some of the largest telescopes in the world, such as the Rosse 6-foot (metal mirrors) , Fig. 6, the Common 5-foot (silver on glass) , the Melbourne 4-foot (metal mirrors, Cassegrain form) , and the 5-foot constructed by Mr. Ritchey for the Yerkes Observatory. Probably [pg 13] the most celebrated, as it was also the first of these monsters, was the 4-foot telescope of Sir William Herschel, made by himself on the principle which goes by his name. ”

“ It is quite possible that there are many people whose sole opportunity of looking through a telescope is the penny peep through the instrument of some itinerant showman, who may have seen more of these than an active astronomer in a lifetime; while as to 'discoveries,' these lie no more within the scope of our national observatory than do geographical discoveries within that of the captain and officers of an ocean liner.
If it is not to afford the astronomer beautiful spectacles, nor to enable him to make thrilling discoveries, what is the purpose of Greenwich Observatory? ”

“ And beside the enjoyment of all this entrancing spectacle of celestial beauty, the fortunate astronomer sits at his telescope and discovers—always he discovers.
This, or something like it, is a very popular conception of an astronomer's experiences and duty; and consequently many, when they are told that 'discoveries' are not made at Greenwich, are inclined to consider that the Observatory has failed in its purpose. An astronomer without 'discoveries' to his record is like an angler who casts all day and comes home without fish—obviously an idle or incompetent person. ”

“ Just as the century is drawing to its close, the Yerkes telescope has begun to enter on its sublime task of exhibiting the heavens under greater advantages than have ever been previously afforded to any astronomers since the world began. ”

“ The building is by far the largest on the ground, but in little accord with the popular idea of an astronomer as perpetually looking through a telescope, carries but a single dome; its best rooms being set apart as 'computing rooms,' for the use of those members of the staff who are employed in the calculations and other clerical work, which form, after all, much the greater portion of the Observatory routine.
An observer with the transit instrument, for instance, will take only three or four minutes to make a complete determination of the place of a single star. ”

“ It has been invariably my own intention to maintain the principles of the long-established system in perfect integrity; varying the instruments, the modes of employing them, and the modes of utilizing the observations of calculation and publication, as the progress of science might seem to require.'
The result of this keen appreciation of the essential continuity of the Astronomer Royalship has been that it is to Airy, more than to any of his predecessors, or than to all of them put together, that the high reputation of Greenwich Observatory is due. ”

“ That stern disciplinarian asked what business the assistant had to be there on his free night, and on being told he was 'searching for new planets,' he was severely reprimanded and ordered to discontinue at once. A similar energy would not meet so gruff a discouragement to-day; but the routine work so fully occupies both staff and telescopes that an assistant may be most thoroughly devoted to his science, and yet pass a decade at the Observatory without ever seeing those 'show places' of the sky which an amateur would have run over in the first week after receiving his telescope. ”

“ But before looking through the great tube, the professor, with quite unintended, but most dramatic effect, called our attention to a black-looking object at the base of the great pier, on which the telescope stands. It was like an altar, as we saw it in the dimness, but a lantern flash upon the front showed us it was a monument above the last resting-place of James Lick, by whose munificent bequest of seven hundred thousand dollars, the Observatory on Mount Hamilton, with all its wonderful instruments, has been established for all time. ”

“ History will be just to his memory, and will not fail to record his early interest and strenuous zeal for the advancement of astronomical science, and the influence his eloquence and untiring perseverance, in illustrating its importance with an unsurpassed array of appropriate learning, exerted on the public mind in the United States, not only in effecting the establishment of other Astronomical Observatories, but absolutely compelling party spirit, notwithstanding its open, bitter animosity, to lay the foundation of that Observatory which now bears the name of "National." ”

“ In recent times the institution has been marked by an energy and a progressiveness that go far to atone for its former deficiencies. The successors of Leverrier have known where to draw the line between routine, on the one side, and initiative on the part of the assistants, on the other. Probably no other observatory in the world has so many able and well-trained young men, who work partly on their own account, and partly in a regular routine. In the direction of physical astronomy the observatory is especially active, and it may be expected in the future to justify its historic reputation. ”

“ In the main, double-star astronomy has been in the hands of amateurs, at least in England. But the discovery in recent years of many pairs so close that a telescope of the largest size is required for their successful observation, has put an important section of double stars beyond the reach of most private observers, and therefore the great telescope at Greenwich is now mainly devoted to their study. The Astronomer Royal, therefore, soon after the completion of the great equatorial of 28-inches aperture placed in the south-east dome, added this work to the Observatory programme. ”

“ This was a fatal mistake, and one which it is very hard to understand how any one with a real interest in the science could have made. Men who had the spirit of 'drudges,' to whom observation was a mere 'mechanical act,' and calculation a 'dull process,' were not likely to maintain the honour of the Observatory, particularly under an absentee Astronomer Royal. ”

“ Nor have even the beautiful photographs of the Paris, Lick, and Yerkes Observatories superseded as yet the work of the human eye and hand. The best of the Yerkes photographs, taken with a 40-inch refractor, are said to show detail 'sufficiently minute to tax the powers of a 6-inch telescope.' But this can be said only of a very few photographs; and, generally speaking, a good 3-inch glass will show more detail than [pg 123] can be seen on any but a few exceptionally good negatives. ”

“ In the early observations of Mr. Bond at Cambridge, priority was given to the work begun at Dorchester for the naval department. In the college record a considerable part of the routine is classed as meteorology, with reference, chiefly, to the earth’s magnetism. The scheme of observation in this department was, however, much broadened, and in this the observatory appears to have performed its first notable service to pure science and to have assumed a place that gave it international recognition. ”

“ True to the traditions which have brought Greenwich its great success, the Astronomer Royal reiterates in this Report the importance of holding fast to "the fundamental idea—"that of meridional observations; and he indicates that if the force of the observatory must be reduced, that reduction should take place in the photographic and spectroscopic work. He says truly that "the [Royal] Observatory is not the place for new physical investigations," but that it is "well adapted for following out any which . . . have been reduced to laws susceptible of verification by daily observation." ”

“ Soon, under the guidance of the good genius so invoked, the secrets of the place begin to reveal themselves.
The part of the Observatory so conspicuous from without is the portion least used within. When it was designed by Christopher Wren, the general belief was that such buildings should be lofty, that the observer might be raised toward the heavenly bodies whose motions he was to watch. More modern science has taught its disciples better; and in Greenwich—which is an eminently practical Observatory—the working part of the building is found crouching behind the loftier towers. ”

“ There is no time for the watcher to spend in what the outsider would regard as 'discovery'; such as sweeping for comets or asteroids, hunting for variable stars, sketching planets, and so forth. Indeed, there is a story current in the Observatory that some fifty years ago, when the tide of asteroid discovery first set in, Airy found an assistant, since famous, working with a telescope on his 'off-duty' night. ”

“ The Royal Observatory at Greenwich has always been, and is now, better equipped in some respects than any other observatory, as might be expected from its deservedly great reputation; but to possess the largest existing telescope has never been one of its ambitions. The instruments in which it takes most pride are remarkable for their steadiness and accuracy rather than for their size;not having suitable telescope at Greenwich and at that time the best telescope possessed by the observatory was not, in Airy’s opinion, large enough to detect the planet with certainty. ”

“ It is specially remarkable among all the similar institutions in the world for the continuity of its labours for several generations. Greenwich Observatory was founded in 1675 for the promotion of astronomy and navigation, and the observations have from the first been specially arranged with the object of determining with the greatest accuracy the positions of the principal fixed stars, the sun, the moon, and the planets. ”

“ There was none in the world that filled all the requirements, and Prof. Bond invented and made one. It is in use, unchanged, to this day, and by means of its ingeniously combined wheels, cogs and pulleys the17 observer can quickly and easily place himself anywhere along the vertical quarter circle and horizontal full circle traversed by the eye-piece of the telescope.
Prior to 1845 a transfer of 12 chronometers to and from Greenwich, Eng., had been made by Prof. Bond and Commodore Owen, for the determination of the longitude of the observatory. ”

“ Before the stars can safely be employed as route-marks in the sky, their movements must accordingly be tabulated, and research into the method of such movements inevitably follows. We perceive then that the fundamental problems of sidereal science are closely linked up with the elementary and indispensable procedures of celestial measurement.
The history of the Greenwich observatory is one of strenuous efforts for refinement, stimulated by the growing stringency of theoretical necessities. ”