Abstract
AN article with ifcra title by H. P. Wilkins, an assiduous the moon, who recently produced a 300-in luna map appears in Sky and Telescope of May. Mr. Wilkins has made a ‘thermal eyepiece’ which tiables the heat of the moon to be noted when it is inserted in the focus of his 121/2-in. Newtonian reflector. The instrument consists of a very small light couple suspended between the poles of a permanent magnet, one junction of the couple being at the focus of a positive eyepiece of orthoscopic or monocentric type. It is necessary to suspend the couple freely, and hence in the case of an equatorial mounting the tube or eyepiece should rotate. The apparatus is enclosed in a brass case which fits into the sliding eyepiece tube like an ordinary eyepiece. The couple is made from strips of copper and con-stantan, and the suspension is a very fine quartz thread. Full directions are given about the use of the instrument, the principle of which depends upon the fact that the thermo-electric current produced by the heat of the moon causes the loop to turn in the field of the permanent magnet, and it is possible to judge the relative intensities of radiation from various portions of the lunar surface. The apparatus can be shielded from the heat of the body by interposing a non-conducting sheet of wood or asbestos. Interesting results have been obtained during lunar eclipses, the turning moment of the couple diminishing before the encroachment of the umbra and being reduced to zero during totality. During penumbral eclipses, when the sun, as seen from the moon, appears partially eclipsed by the earth, a diminution of the heat from the moon is noticed. It seems possible for most amateurs with a small mechanical equipment to construct one of these instruments, though many details must be attended to; these are dealt with very fully in the article.
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A Thermal Eyepiece for the Telescope. Nature 158, 373 (1946). https://doi.org/10.1038/158373c0
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DOI: https://doi.org/10.1038/158373c0