ASTRONOMICAL.

Taranaki Daily News, 23 November 1920, Page 7

ASTRONOMICAL.

NEW PLYMOUTH OBSERVATORY. The observatory continues to be visited by many people on such evenings as permit of celestial observations being made. Unfortunately the recent cloudy weather has interfered on a number of occasions, yet every opportunity has been eagerly seized by those present, and a great deal of interest has been aroused in the minds of many who have never previously had the privilege of .using a powerful telescope. The moon is a prime favorite with all beginners, and, on nights when this orb is under observation, little time has been found to examine other parts of the sky. It is not generally known that quite a small telescope will, if steadily held, reveal all the larger formations visible npon the moon's surface. By such means a good general knowledge of the positions, forms and apparent changes of such features may bo gained. Those who can in their way acquaint themselves with the lunar topography will find it an immense advantage, when they come to use the ia,rge telescope at | the observatory. To many who see the moon in this instrument for the first time, the vast amount of detail brought to view is apt to surprise them to such an extent that they fail to realise what it is they are really looking at. The 1 whole scene is so utterly new and strange to them that they fail to comtprehend at once the meaning of the unwonted sight. Nor is this to be wondered at. It is not easy at first to mentally grasp so strange a scene. Tn the first place the moon is shown upside down in the telescope, so that what one expects to see on the right hand side appears upon the left. Then, except when the lowest magnifying eyeipiece is employed, only part of the visible portions of the moon is in the field of view at one time; consequently the mind does not at once recognise, in the great rugged, indented surface which fills the circular field of view, the familiar object which has shone down upon us from as far back as we can remember. When told that the objects seen are mountains, the mind is again nonplussed, owing to the fact that we are accustomed to see mountains from a horizontal and -lot from a perpendicular point of view. The lunar mountains are seen by us as from an aeroplane; we arc, as it were, looking down upon them, and as they are all, or nearly all, of volcanic origin, we see right into their vast and profound craters. The moon is a globe or spliere, and as it slowly revolves upon its axis, the light from the sun throws the shadows of the mountains before them, with the result that, at whatever part of the sphere the sun is shining, the long shadows cause all objects to stand out in high relief. Astronomers call the region upon I which the sun is rising the terminator, because there the dark portion terminates, and it is within this part, where the first rays of sunlight fall, that all important observations of lunar objects are made. As the sun rises upon any feature its shadow shortens, and finally, when the siur is high above it, disappears altogether, and the object becomes lost to view in the general brightness of the moon's surface. Hence there is very little to be seen when the mnon is full, the terminator having passed round to the further side of our satellite, which side we never see. Recently Mr. J. T. Ward, of Wnnganui, who is an expert in the manufacture of reflecting telescopes, tested the 12-inch mirror owned by the Society. He now reports very favorably of its qualities, and it is to be left in" his care until the funds of the society permit of its being mounted by Mr. Ward and housed upon Marsland Hill. The amount required for ;*%• wetk is about £2OO.