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 232
n it; and at the distance of eight or ten inchesfrom the eye it will appear so large, that it willseem to cover a large building placed within thedistance of a quarter of a mile, in other words,the apparent magnitude of the half-crown held atsuch a distance, will more than equal that of sucha… … I 208 THE PRACTICAL ASTRONOMER. is seen under the small angle FED. B will re-present its apparent magnitude at 4^ yards distantunder the angle HEG, and the circle C, its appa-rent magnitude at 3 yards distant, under the largeangle KEI. This may be otherwise illustrated by the fol-lowing figure. Let…
Astronomy · Astronomical instruments · Telescopes
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