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Updated: May 26, 2025
Galileo's great discovery of Jupiter's four moons was the last word in this connection until September 9th, 1892, when Barnard, using the 36-inch refractor of the Lick Observatory, detected a tiny spot of light closely following the planet. Between its rising and setting there must be an interval of 2-1/2 Jovian days, and two or three full moons.
Many stars previously believed to be single divided under the scrutiny of the Dorpat refractor; while in some cases, one member of a supposed binary system revealed itself as double, thus placing the surprised observer in the unexpected presence of a triple group of suns.
The refractor is a tube made so that you can look through it, but the reflector will be, if you are right, so that you can't look through it, because instead of being at the end, the hole will be in the side. Is that correct?" "Quite right, and you are quite wrong, Tom, for you do not understand the first simple truth in connection with a telescope."
Finally, Professor Barnard, directly measuring with the Yerkes refractor the minute discs presented by the original quartette, obtained the following authentic data concerning them: Diameter of Ceres, 477 miles, albedo = 0·18; diameter of Pallas, 304 miles, albedo = 0·23; diameter of Vesta, 239 miles, albedo = 0·74; diameter of Juno, 120 miles, albedo = 0·45.
The only instruments in this country successfully employed for its detection are, we believe, Dr. Common's 5-foot reflector and Mr. Newall's 25-inch refractor. In the course of his observations on Jupiter at Brussels in 1878, M. Niesten was struck with a rosy cloud attached to a whitish zone beneath the dark southern equatorial band. Its size was enormous.
If my object were to make you fear and tremble, I should tell you that on the evening of the 30th I was sweeping within a few degrees of your prize. I merely throw out the hint for what it is worth. It has been very interesting to watch the motion of this comet among the stars with the great refractor; we could almost see it move. Respectfully, Your obedient servant, Hon.
The instruments employed are an eight inch Voigtlander photographic lens, reground by Alvan Clark & Sons, and Dr. Draper's 11 inch photographic lens, for which Mrs. Draper has provided a new mounting and observatory. The 15 inch refractor belonging to the Harvard College Observatory has also been employed in various experiments with a slit spectroscope, and is again being used as described below.
When Bond rediscovered the dark ring, everything promised that before long the appendage would be visible with telescopes far inferior in power to the great Harvard refractor. Year after year the planet was becoming more favourably placed for observation, while all the time the rings were opening out.
Clouds interposed, and we lost the first contact, but were more fortunate in the end, which was observed as follows: By Mr Wales with Dollond's 3 1/2 foot achromatic refractor, at 3h 28' 39" 1/4 \ By Mr Clerke with Bird's 2 feet |Appa- reflector, at 3 28 52 1/4 |rent And by me with an 18 inch reflector |time. made by Watkins, 3 28 53 1/4 / Latitude of the isle or place of observation, 20° 17' 39" S. Longitude per distance of the sun and moon, and moon and stars, 48 sets, 164° 41' 21" East.
It made, nevertheless, capricious appearances at South Kensington during that autumn, and again October 21, 1894, while in September, 1892, Bélopolsky could obtain no trace of it on orthochromatic plates exposed with the 30-inch Pulkowa refractor. No fluctuations in the hydrogen-spectrum were betrayed by them; but subordinate lines of unknown origin showed alternate fading and vivification.
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