The Observatory, Volume 5Editors of the Observatory, 1882 Some vols. for 1886- include a special issue: Annual companion to the Observatory. |
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Common terms and phrases
aperture appearance April astronomers atmosphere August Axis bands bright lines catalogue centre Christie comet crater dark spots Demainbray determination diameter discovery disk distance drawing E. W. MAUNDER eclipse Ephemeris equator equatoreal belt errors eyepiece faint flexure Greenwich heliometer Hyginus inches instrument JOHN TEBBUTT July June Jupiter Knobel light longitude magnitude marked Mars means measures meridian meteors method minor planets minutes Moon motion nearly nebula Neison nucleus object object-glass observations obtained orbit perihelion period Perseids phenomena photographs photometer planet position prism probably Prof rainband red spot refractor remarkable ring rises Royal Observatory satellites Saturn seen Sept September Society solar parallax spectra spectroscope stars sun-spots Sun's limb tail telescope tion Transit of Venus variable stars visible wedge whilst white spot ΙΟ
Popular passages
Page 159 - The screw is practically perfect and has been tested to ] o fa 0 0 inch without showing error. Neither does it have any appreciable periodic error, and the periodic error due to the mounting and graduated head can be entirely eliminated by a suitable attachment. For showing the production of ghosts by a periodic error, such an error can be introduced to any reasonable amount. Every grating made by the machine is a good one, dividing the 1474 line with ease, but some are better than others.
Page 157 - I hope to make a practically perfect screw, and so important did the problem seem, that I immediately set Mr. Schneider, the instrument maker of the university, at work at one. The operation seemed so successful, that I immediately designed the remainder of the machine, and have now had the pleasure since Christmas of trying it. The screw is practically perfect, not by accident, but because of the new process for making it, and I have not yet been able to detect an error so great as l-loo,oooth part...
Page 165 - The time, if the observer is alone, may be taken by a chronograph or stop-watch. Great accuracy is not needed, since if ten seconds correspond to one magnitude, it will only be necessary to observe the time to single seconds. The best method is to employ an assistant to record and take the time from a chronometer or clock. If the stars are observed in zones, the transits over the bar serve to identify or locate them as well as to determine their light. A wedge inserted in the field of a transit instrument...
Page 181 - The most useful branch of astronomy has hitherto been that which, treating of the positions and motions of the heavenly bodies, is practically applied to the determination of geographical positions on land and at sea. The Greenwich Observatory has, during the past century, been so far the largest contributor in this direction as to give rise to the remark that, if this branch of astronomy were entirely lost, it could be reconstructed from the Greenwich observations alone.
Page 165 - Acad. XVI. 364). Very perfect definition would not be required, since it would affect all the stars equally. To an amateur who would regard the complexity of an instrument as a serious objection to it, a means is now afforded of easily reducing his estimates of magnitude to an absolute system, and thus rendering them of real value.
Page 163 - The stars must always be kept in the same part of the field, or the readings will not be comparable. By a long wedge the error from this source will be reduced. A second wedge in the reversed position will render the absorption uniform throughout the field. Instead of keeping the star in the same place by means of clockwork, the edges of the wedge may be placed parallel to the path of the star, when the effect of its motion will be insensible. To obtain the best results the work should be made purely...
Page 96 - X 4340, is of the same length as the slit, and where it intersects the spectrum of the trapezium stars, a duplication of effect is visible. If this is not due to flickering motion in the atmosphere, it would indicate that hydrogen gas was present even between the eye and the trapezium.
Page 136 - There were only 2 days out of 200 on which the sun's disk was observed to be free from spots. There has been a large increase in...
Page 255 - The physical appearance of the comet, which like that of 1843, and unlike that of 1880, showed at first a decided nucleus, together with the intimation of a period very considerably greater than that of the interval from 1880, January 27, the date of perihelion of the 1880 comet...
Page 158 - ... and grating are attached end to end, thus forming a diameter of the circle with the eyepiece at the centre of curvature of the mirror, and the rod carrying the slit alone movable. In this case the spectrum as viewed by the eyepiece is normal, and when a micrometer is used the value of a division of its head in wave-lengths does not depend on the position of the slit, but is simply proportional to the order of the spectrum, so that it need be determined once only. Furthermore, if the eyepiece...