Half-hours with the Telescope: Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction

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R. Hardwicke, 1868 - Astronomy - 109 pages

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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...
Page 11 - To remedy this defect, achromatic lenses were formed by the union of a convex lens of crown glass with a concave lens of flint glass.

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