The practical astronomer : comprising illustrations of light and colours, practical descriptions of all kinds of telescopes, the use of the equatorial-transit, circular, and other astronomical instruments, a particular account of the Earl of Rosse's large telescopes, and other topics connected with astronomy (1845)
Dick, Thomas, 1774-1857 · London : Seeley, Burnside, and Seeley · leaf 261
fectionsconnected with common refracting telescopes. The first imperfection to which I allude is this,that spherical surfaces do not refract the rays oflight accurately to a point; and hence the imageformed by a single convex lens is not perfectlyaccurate and distinct. The rays which pass nearthe… … lens and ~Ee an object, the point E of which cor-responds with the axis, and sends forth the raysEM, EN, EA, &c, all of which reach the surfaceof the glass, but in different parts. It is manifestthat the ray EA which passes through the middleof the glass, suffers no refraction. The rays EM,EM,…
Astronomy · Astronomical instruments · Telescopes
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