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61 Cygni Albireo Algol Almanac alt-azimuth Andromeda aperture appears Arcturus astronomical axis blue brilliant Cassiopeia Castor centre cluster companion components constellation conveniently convex lens Cygni Cygnus dark Dawes diameter directed disc distance distinct vision double star easy double ecliptic emergent pencils Equuleus exhibit eye-glass eye-piece eye-tube favourable field of view finder focal length focus formed Galilean Telescope glass HALF-HOUR heavens Herschel horizon hour Howlett instrument interesting inverted Jupiter Jupiter's latter light look low power magnitude maps Mars Mercury meridian method Milky Mizar moderate power moon motion naked eye nebula northern noticed object object-glass observer Ophiuchus orange Orion pass planet Pole-star position powerful telescope quadrature red star right ascension rings satellites Saturn Scorpionis screen seen Serpentis shadow shown in Plate Sirius smaller solar spherical aberration spot sun's supposed tele telescopist trapezium tube turn variable Vega visible wide double yellow zenith
Page 84 - Hercynian mountains, within a circumvallation called Lichtenburg. The brightest portion of the whole lunar disc is Aristarchus, the peaks of which shine often like stars, when the mountain is within the unillumined portion of the moon. The darkest regions are Grimaldi and Endymion, and the great plain called Plato by modern astronomers — but, by Hevelius, the Greater Black Lake. But although there are varieties, there has never yet been detected any variation of colour.
Page 14 - K e' respectively work, are so fastened by elastic cords that an upward pressure on the handle h, or a downward pressure on the handle h', at once releases the endless screw or the crown-wheel respectively, so that the telescope can be swept at once through any desired angle in altitude or azimuth.
Page 83 - Linne — where lately signs were supposed to have been seen of a process of volcanic eruption—will prove an exception to this rule, remains to be seen. The evidence seems to me strongly to favour the supposition of a change of some sort having taken place in this neighbourhood. The sort of scrutiny required for the discovery of changes, or for the determination of their extent, is far too close and laborious to be attractive to the general observer. Yet the kind of observation which avails best...
Page 84 - ... tone, but in the photographic quality of the light they reflect towards the earth. Some of the seas exhibit a greenish tint, as the Sea of Serenity and the Sea of Humours. Where there is a central mountain within a circular depression, the surrounding plain is generally of a bluish steel-grey colour. There is a region called the Marsh of Sleep, which exhibits a pale red tint, a colour seen also near the Hyrcinian mountains, within a circumvallation called Lichtenburg.
Page 83 - Maraldi, precisely because they are now recognized as snow-covered regions, increasing in the martial winter and diminishing in the martial summer. It is in this relation that we have spoken of the moon as the most disappointing object of astronomical observation. For two centuries and a half, her face has been scanned with the closest possible scrutiny ; her features have been portrayed in elaborate maps ; many an astronomer has given a large portion of his life to the work of examining craters,...
Page 39 - ... we could plainly see that all about the trapezium is a mass of stars ; the rest of the nebula also abounding with...