Description and use of a new constructed equatorial telescope or portable observatory / made by E. Nairne.
- Edward Nairne
- Date:
- 1771
Licence: Public Domain Mark
Credit: Description and use of a new constructed equatorial telescope or portable observatory / made by E. Nairne. Source: Wellcome Collection.
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![[4] the convenience of better feeing the meridian dis¬ tance {hewn by the vernier ; On the upper part of the equatorial plate is the plate K ; upon this plate K, are fixed the two fupporters M M, which fup- port the axis N, under which is fattened the femi- circle of declination O, divided into half degrees* and has a vernier index fubdividing it to 3 minutes ; on the upper part of this axis, is fixed an achromatic Telefcope P, which magnifies about 50 times; to the eye End of this Telefcope, is applied a fmall reflecting fpeculum making an angle of 450 with the axis of the telefcope, whereby objeCts that are in the zenith or any other altitude may be obferved, with¬ out putting the body in any inconvenient pofition ; to the under part of the axis N, is fattened a brafs arm carrying the weight Q, which counterbalances the telefcope, and the brafs work annexed to it; whilft the weights R R counterbalance in like manner the whole bf the inftrument that is moveable on the equatorial axis, fo that whatever pofition the inftru- ment is put in, it will there remain, being perfectly balanced; the four motions of this inftrument may, when required, be moved extreamly flow, by means of the indented edges of the circle and fe- micircles, and the fcrews or worms to which the handles are fixed, viz. that for the horizontal mo¬ tion marked S, called the horizontal handle, that marked T the handle of latitude, V the equatorial handle, and W the declination handle. To adjuft the inftrument for obfervation, the firfi: thing to be done is to make the horizontal plate D level, by means of the fpirit level* and the three ad- jutting fcsews at the bottom of the ftand; this being done,](https://iiif.wellcomecollection.org/image/b30368509_0004.jp2/full/800%2C/0/default.jpg)
