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THE INTELLECTUAL OBSERVER.
MARS DURING THE LATE OPPOSITION.
BY JOHN BROWNING, F.R.A.S.
(With a Coloured Plate.)
Though Mars is, with the exception of Mercury, the smallest of the chief planets in the solar system, exceeding but little in magnitude Titan, the sixth of Saturn's satellites, yet it has always excited great interest, from the fact of its being the only planetary body which in its physical conformation bears a close resemblance to that of our earth.
With a good telescope we see its surface mapped out into What are believed to be continents and seas, though these would seem to be distributed in the contrary order to that which they occupy on our globe-the great seas being situated near the poles of the planet, while a broad belt of land surrounds it at me, equator. Near the poles, but not corresponding exactly with them, are seen ice and snow, which melt as the poles are respectively presented more directly towards the sun. Like our earth, Mars has a cloudy atmosphere, betokening the presence of both air and water.
he accompanying drawings of Mars, so beautifully rendered ours, were made in Mr. Barnes's Observatory, at Upper way, with his telescope, an equatoreal reflector of my make, having a silvered-glass speculum, 8} inches in er, which was parabolised for me by Mr. With. Achc eye-pieces of positive construction were alone employed.
wer used was generally 300, but, occasionally, on
nuen the air was unusually steady, I have used powe as high as 600, with great advantage.
persons who have seen the original drawings, have such questions to me as these :-But, did you get tion as you have represented ? Could you really all those details ? To answer these questions I must he method I adopted in making the drawings.
er of circles were previously prepared, each being a
diameter, which w romatic eye-pieces The power use
Many persons addressed such quest such definition as yo make out all those deta describe the method
A number of circ
white disk on a black ground. On looking at the planet through the telescope, it frequently happened that only the general character of the markings upon it were discernible. The most prominent of these markings were at once noted on one of the prepared circles, as quickly as possible, consistent with accurate estimation and determination of their position. It is important that this portion of the work should be promptly executed, because the position of the markings rapidly changes with the rotation of the planet.
Having obtained the outline of the principal markings in the manner above described, intervals of good definition were watched for, and upon their occurring, details of minuter markings, colours, and shadows were successively filled in, until in about an hour the drawing was completed.
It will be understood that a drawing made in the manner stated will show many features of interest that would escape notice in a cursory observation. It will, in fact, represent the most that can be made out by patient watching, with a telescope of the aperture employed on the particular night.
In the present drawings the planet is shown as it was seen in the telescope. As inverting eye-pieces were alone used, the lower white markings always represent the ice or snow on the north pole of the planet, while the smaller light patches on the upper part of some of the disks indicate the ice near the south pole. I have made nearly thirty sketches at the telescope, but I have carefully copied only thirteen. These were all made when the air was tolerably steady, and the definition so good that I could work well with powers above 200. Of this number eight of the most interesting have been selected for representation.
When several sketches were made on the same evening, they were taken at intervals of two hours, if the weather permitted. In only one instance have I failed to make out that the form of the markings was permanent, due allowance being made for the effect of perspective in foreshortening them as they approached the edge of the disk.
It is highly probable that in the view of the planet taken on February 16th, at 6:45, the two pointed markings on the extreme left, one above, and the other below the equator, would have been seen united if they could have been observed when they were on the centre of the disk. This drawing would then have agreed pretty closely with one of Mr. Dawes's views engraved in the “Astronomical Register for September, 1865.
The colour of the body of Mars I have found vary from rose-madder to burnt ochre, the colour appearing ruddiest when there was most mist in our atmosphere. The comparative absence of the ruddy colour towards the edges of the