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Diagram of the ball and ring system of Saturn, showing the projected positions and limits of the condensations.
The lines A, B, B, A show where the centres of the condensations fall. The dotted
lines a, a, b, b, b, b, a, a show the limits of the condensations.
In Monthly Notices for November 14, 1862, vol. xxiii. pp. 87-88, there are some observations of Saturn at the time of the disappearance of the ring in that year made at Greenwich and Pulkowa. In both these there are distinct references to luminous appendages, which seem roughly to be the same seen at the observations of this year-1907. The descriptions are not quite in satisfactory accord with their appearance as seen to-day. The ring was supposed to have disappeared on May 17, 1862, by the Sun going north, and to have remained invisible until August 12. At Pulkowa the descriptions seem to indicate only two appendages, one on the preceding, the other on the following ansa. not seem to have been perfectly symmetrical. The Pulkowa observations are:
"1862 May 20. The aspect of the luminous appendages has not varied since last night, with this difference only-that I estimated the length of the preceding side as 0.65 and the following as o'5 of the planet's diameter.
"1862 May 21. Images good. Estimated extent of luminous appendages:-Preceding side o·6, following side o ̊4, of the planet's diameter; also the intensity of the light appears much more feeble on the following side. The size of these appendages increased in the neighbourhood of the planet, giving them the form of sharp wedges.
"1862 May 22. Images less favourable than yesterday. Extent of luminous appendages on preceding side o6 and on following side o5 of the planet's diameter.
"1862 June 3. Image very bad, yet the luminous appendages are still distinctly visible. It appears that the length of the following ansa is a little the greater, but this is not certain."
The Greenwich observations are:
"1862 May 17. The ring beyond the planet at times just visible on the left of the disk, but on the right only a small faint spot could be seen in the plane of the ring, about the diameter of the disk from the planet's limb. I should have suspected this was a satellite but for its elongated shape. Sky very hazy.
"1862 May 19. Saturn very well seen. The ring distinctly
visible on the left of the disk, and fairly but not so distinctly visible on the right. Where it crosses the disk, the under edge is much sharper and better defined than the upper edge.
"1862 May 20. Saturn very well seen; the ring distinctly visible, appearing brighter than it did last night. The Greenwich observations were made by Mr. Carpenter."
There are also some observations by Mr. Wray in the same number of the Monthly Notices, in which he saw something of the kind in December of 1861 and January of 1862 with a 7-in. refractor.
1907 November 25.
Additional Observations of the Disappearances and Reappearances
of the Rings of Saturn in 1907-8, made with the 40-inch Refractor of the Yerkes Observatory. By E. E. Barnard.
1907 Nov. 23-with 12-inch telescope, 6b 15m, power 150±. I could see the two condensations on the preceding part of the ring. They were fairly distinct, but faint. Could scarcely see them on the following side.
7h30m-using a higher power. The ring and condensations were not so well seen. A satellite closing in following, mixed its light with the condensations on that side. With the low power could see the two condensations on the preceding ansa very distinctly. They appeared equal in brightness. The inner one joined up to the planet with but little change of brightness. There was no doubt but that the following ansa and condensations were fainter than the preceding. The satellite interfered, however. The sky was clear and good, but the image was unsteady. The trace on the ball was apparently dark and without irregularities.
Nov. 24. 5h 11m. The condensations were easy. There were two satellites, one preceding and one following, that interfered. The condensations were of equal brightness, both preceding and following. The inuer one preceding was bright to the ball. The entire ring was visible with or without the occulter. Seeing = 2 (on a scale of 5). Lost in clouds.
8h 46m. Thinning down near Saturn. The following ansa was certainly the brighter. There was a faint satellite (Mimas) following the following end of the ring. The outer condensation near it was twice as bright as the satellite. Seeing = 1. The full extent of the ring was quite conspicuous when best seen.
9h 8m-with the 12-inch telescope. Could see the condensations. Both Mr. Sullivan and I decided that the following side was the brighter. Seeing poor with 12-inch. (Back to 40-inch.) There was no question but that the following ansa was the brighter. The ring between the condensations was faint. The outer condensation following was two times as bright as the faint satellite following (Mimas). In each case the outer and inner condensations were of equal brightness. Seeing very bad.
Nov. 25. 4h 55m. The condensations were of equal brightness. The space between them was almost discontinuous.
5h 25m. Distance between the centres of the preceding condensations
́4′′·60 (6) [4′′ ́44].
Distance between the centres of the following condensations
Seeing very poor.
4′′ 51 (6) [4′′ 35].
Went to the 12-inch telescope. Could faintly see the rings and condensations-very faint compared with the view in the 40-inch.
Nov. 26. 5h 55m. Seeing fair for moments. The condensations
were very bright, but the ring between them was very faint, and all but discontinuous.
6h 25m. The small satellite following was the same brightness as the inner condensation, but very slightly brighter than the outer The following ansa was considerably brighter than the preceding. I could see the ring beyond the outer condensation following, I think, all of it, but it was extremely faint. The condensations were about the thickness of the diameter of the bright satellite following. The inner condensations were a little brighter at their outer ends. Seeing
6h 45m. The bright satellite was half a magnitude brighter than the outer condensation.
6h 50m. The outer condensation was exactly midway between the satellite and the following limb. The following ansa and condensations were certainly brighter than the preceding. They were all conspicuous with the planet unobscured. When seen best the condensations appeared to become narrower.
Nov. 28. 5h 4m. Seeing very poor. The ring and condensations were conspicuous.
5h 24m. There was a small satellite (Tethys) just north of the ring, and about midway between the condensations following. I think the following ansa was the brighter.
6h 49m. There was a small satellite between the two condensations preceding, nearer the outer one. There was a bright satellite close preceding the end of the ring in line with it. There was a similar satellite at the preceding end of the ring a little north. These satellites were half a magnitude brighter than the condensations. I think the inner condensation following was slightly brighter than the outer one.
6h 59m. Seeing very poor. There was a very faint satellite (Enceladus?) then visible at the preceding end of the ring, close south following the brighter satellite. The seeing was very poor. I could not make out any details on the ball. 8h 54m. The seeing better, though the following ansa was, I think, the brighter. condensations were of the same brightness. up to the ball with almost full brightness. The space between them looked to be a little less than on some previous nights.
planet was low. The The inner and outer The inner ones joined
Dec. 3. 7h 42m. The condensations were quite bright.
27′′·25 (8) [26·63].
From preceding limb to outer condensation
7" 55 (8) [7:38].
The inner condensation was bright up to the planet. Could not make much out of it on account of the blurring. I don't think there had been any change in the condensations. brighter than the small satellite (Tethys ?) preceding.