Practical observations on telescopes.

  • William Kitchiner
Date:
1815
Catalogue details

Licence: Public Domain Mark

Credit: Practical observations on telescopes. Source: Wellcome Collection.

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    nify more than forty, it will show the face of the moon, and leave a margin round it. There is a vulgar error almost universally prevalent, that Saturn will bear a higher magnifying power than Jupiter, notwith¬ standing Jupiter is a much brighter object than Saturn. My own experience is diametrically opposite; for, as common sense would teach any thinking mind, Jupiter will bear a high power better than Saturn, in proportion as he shines with more vivid light*. And the reason why this vulgar error is so universal, I fancy, must be because Jupiter is so bright an object, that only a very perfect glass will show it well; whereas Saturn, from its distance and dingy colour, will look * Though many optical writers have offered obser¬ vations on the requisite diameter, &c. of the pencil of rays, none, I believe, have considered the quality of them. A pencil of rays, of the 50th of an inch dia¬ meter, proceeding from an intensely bright object, i. e. a fixed star, will stimulate the optic nerve as much as a pencil of the 20th of an inch diameter, from a body that is badly illuminated.
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