Half-hours with the Telescope - Being a Popular Guide to the Use of the Telescope as a - Means of Amusement and Instruction. by Richard Anthony Proctor
page 7 of 115 (06%)
page 7 of 115 (06%)
|
of Mars with anything like the distinctness I have here given to them.
If he place the plate at a distance of six or seven yards he will see the views more nearly as Mars is likely to appear in a good three-inch aperture. The chart of Mars is a reduction of one I have constructed from views by Mr. Dawes. I believe that nearly all the features included in the chart are permanent, though not always visible. I take this opportunity of noting that the eighteen orthographic pictures of Mars presented with my shilling chart are to be looked on rather as maps than as representing telescopic views. They illustrate usefully the varying presentation of Mars towards the earth. The observer can obtain other such illustrations for himself by filling in outlines, traced from those given at the foot of Plate VI., with details from the chart. It is to be noted that Mars varies in presentation, not only as respects the greater or less opening out of his equator towards the north or south, but as respects the apparent slope of his polar axis to the right or left. The four projections as shown, or inverted, or seen from the back of the plate (held up to the light) give presentations of Mars towards the sun at twelve periods of the Martial year,--viz., at the autumnal and vernal equinoxes, at the two solstices, and at intermediate periods corresponding to our terrestrial months. In fact, by means of these projections one might readily form a series of sun-views of Mars resembling my 'Sun-views of the Earth.' In the first view of Jupiter it is to be remarked that the three satellites outside the disc are supposed to be moving in directions appreciably parallel to the belts on the disc--the upper satellites from right to left, the lower one from left to right. In general the |
|