Royal 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. ”

“ 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." ”

“ In the thirteen years ending 1689, he made 20,000 observations, and had revised single-handed the whole of the theories and tables of the heavenly bodies then in use.
In 1688 the death of his father brought him a considerable accession of means, and, far more important, the assistance of Abraham Sharp, [1] the first and most distinguished of the long list of Greenwich assistants, men who, though far less well known than the Astronomers Royal, have contributed scarcely less in their own field to the high reputation of the Observatory. ”

“ The general public is apt to lay stress rather on the first than on the second, and to think it rather a reproach to Greenwich that it has taken no part in such explorations. Experience has, however, shown that they may be safely left to amateur activity, whilst the monotonous drudgery of the observation of minor planets can only be properly carried out in a permanent institution.
The observation of these minute bodies with the transit circle and altazimuth is attended with some difficulties; but precise observations of various objects may be made with an equatorial ”

“ 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. ”

“ Work such as this is most interesting to the general public, and is followed with much devotion by many amateur astronomers. For that very reason it does not form an integral part of the programme of our State observatory. But work which is necessary for the general good, or for the advancement of the science, and which demands observations carried on continuously for many years, and strict unity of instruments and methods, cannot possibly be left to chance individual zeal, and is therefore rightly made the first object at Greenwich. ”

“ In this activity Greenwich Observatory practically took no part. Airy, ever mindful of the original purpose of the Observatory, and deeply imbued with views similar to those which we have quoted from Bessel, considered that the new science lay outside the scope of his duties, until in Mr., now Sir William,
[271] Huggins's skilful hands the spectroscope showed itself not only as a means for determining the condition and constitution of the stars, but also their movements—until, in short, it had shown itself as an astronomical instrument even within Bessel's narrow definition. ”

“ Many distinguished men have held the important post of Astronomer-Royal at Greenwich, including Flamsteed, Halley, Bradley, and Sir George Airey, under whose enlightened auspices the observatory has won first rank amongst similar institutions elsewhere, a position it seems likely long to maintain if its interests are protected from the dangers that have recently begun to threaten them. ”

“ For the sailor it will always be sufficient to know the places of a mere handful of the brightest stars, and the vast majority of those in the great photographic map will never be visible in the little portable telescope of the sailor's sextant. But it will be freely admitted that in the case of an enterprise of this nature, in which the observatories of so many different nations were uniting, and which was so precisely on the lines of its original charter, though an extension of it, it was impossible for Greenwich to hold back on the plea that the work was not entirely utilitarian. ”

“ As the largest telescope at Greenwich was only 7 inches in aperture up to 1859, and only 123/4 inches up to 1893, it is only very recently that it has been able to take any very substantial part in satellite measures. But since the Thompson photographic telescope was set up, it has been found that a photograph of Neptune and its satellite can be taken in considerably less time than a complete set of direct measures can be made, whilst the photograph, which can be measured at leisure during the day, gives distinctly the more accurate results. ”

“ If we believe, as surely we must, that not only the moral and the physical progress of mankind is watched over and controlled by God's good Providence, but its intellectual progress as well, then there can be no doubt that John Flamsteed was raised up at this particular time, not merely to found Greenwich Observatory, and to assist the solution of the problem of the longitude at sea, but also, and chiefly, to become the auxiliary to a far greater mind, the journeyman to a true master-builder. ”

“ Roughly speaking, therefore,
[123] we may say that three-fourths of the present Observatory has been added during the nineteen years of the present Astronomer Royal. One exceedingly important improvement should not be overlooked. Airy observed little himself whilst at Greenwich, and had an inadequate idea of the necessity for room in a dome and breadth in a shutter-opening. With the sole exception, perhaps, of the transit circle, every instrument set up by Airy was crammed into too small a dome or looked out through too narrow an opening. ”

“ From now onwards the places of stars were referred to the pole, not to the zenith; the zero being obtained from measures on circumpolar stars. Standard stars were used for giving the clock error. In 1816 a new transit instrument, by Troughton, was added, and from this date the Greenwich star places have maintained the very highest accuracy.
George Biddell Airy, Seventh Astronomer Royal, [4] commenced his Greenwich labours in 1835. His first and greatest reformation in the work of the observatory was one he had already established at Cambridge, and is now universally adopted. ”

“ The movements of the stars towards us, or away from us, are, in general, extremely slow as compared with the speed of light itself; and hence the apparent shift in the position of a line is only perceptible when a very powerful spectroscope is used. This means that the feeble light of a star has to be spread out into a great length of spectrum, and a very powerful telescope is necessary. The work of observing the motions of stars in the line of sight was started at Greenwich in 1875, the 'Great Equatorial' being devoted to it. ”

“ It is not every field of astronomy that is cultivated at Greenwich. The search for comets and for 'pocket planets' forms no part of its programme; and the occupation so fascinating to those who take it up, of drawing the details on the surfaces of the moon, Mars, Jupiter, or Saturn, has been but little followed. Such work is here incidental, not fundamental, and the same may be said of certain spectroscopic observations of new or variable stars, and of many similar subjects. ”

“ 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. ”

“ More [202] wonderful still, a comparison of the star-places, obtained at a number of observatories, including Greenwich, has shown that the earth is continually changing her axis of rotation. And so the star-places determined at Greenwich have shown that the north pole of the earth, 2600 miles away, moves about in an irregular curve about thirty feet in radius.
Nothing is stable, nothing is immovable, nothing is constant. The astronomer even finds that his own presence near the instrument is sufficient to disturb it. ”

“ As an astronomer, his services to the science rank higher than those of his predecessor; but as Astronomer Royal, as director, that is to say, of Greenwich Observatory, he by no means accomplished as much as Flamsteed had done. Professor Grant, in his History of Physical Astronomy, says that he seems to have undervalued those habits of minute attention which are indispensable to the attainment of a high degree of excellence in the practice of astronomical observation. ”

“ Greenwich, enters the object-glass, passes downwards to a basin of mercury, and is reflected upwards from the surface of the mercury to a little prism placed over the centre of the object-glass, from which it is reflected again into the eye-piece. By means of this telescope the distance of the star Gamma Draconis from the zenith could be measured very exactly, and, consequently, the changes in the apparent position of the star due to aberration, parallax, and other causes could be very exactly followed, and the corrections to be applied on account of these causes precisely determined. ”

“ 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. ”

“ The Observatory domain at present is fully two hundred yards in greatest length, with an average breadth of about sixty. Nearly the whole of this accession took place under the directorates of Pond and Airy. The present instruments are, therefore, as a rule, the more modern in direct proportion to their distance from the Octagon Room—the old original Observatory. There is one notable exception. The very first extension of the Observatory buildings, made in the time of Halley, the second Astronomer Royal, consisted in the setting up of a strong pier, to carry two quadrant telescopes. ”

“ All the early observatories of Europe seem to have been built as temples to Urania, and not as working-chambers of science. The Royal Observatory at Greenwich, the Imperial Observatory of Paris, and the beautiful structure on Calton Hill, Edinboro', were at first wholly useless as observatories. That of Greenwich had no steadiness, while every pillar in the astronomical temple of Edinboro', though it may tell of the enlightenment of Greece, hides the light of the stars from the Scottish observer. ”

“ It takes much more room than the German form, and the telescope cannot be directed precisely to the pole. But the instrument is symmetrical, there is no deadweight, and the telescope can follow a star from rising to setting without having to be reversed on crossing the meridian.
The great stability of the English form of mounting, therefore, commended it very highly to Airy, and he designed the great Northumberland equatorial of the Cambridge Observatory on that plan, as well as one for the Liverpool Observatory at Bidston, and in 1858 the S.-E. equatorial at Greenwich. ”

“ This simply means that the originators of the constellations lived in 40° north latitude, and stars within 40° of their south pole never rose above their horizon, and consequently were never seen, and could not be mapped, by them. In like manner, the star census taken at Greenwich Observatory does not include the whole sky, but leaves a space some 52° in radius round our south pole. Since the latitude of Greenwich is nearly 52° north, stars within that distance of [185] the south pole do not rise above our horizon, and are never seen here. ”

“ There is no enterprising head of an observatory but must feel cramped in his designs if he can command no more than 14 or 15 inches of aperture, and he aspires to greater instrumental capacity, not merely with a view to the chances of discovery, but for the steady prosecution of some legitimate line of inquiry. Thus projects of telescope-building on a large scale are rife, and some obtain realisation year by year. Sir Howard Grubb finished in 1893 a 28-inch achromatic for the Royal Observatory, Greenwich ”