PHOTOGRAPHING SHOOTING STARS.

Press, Volume LIX, Issue 17700, 28 February 1923, Page 5

PHOTOGRAPHING SHOOTING STARS.

/Tt„ T)r \V J- S. Lockyor. Director o ? y th? Norman Lochyer Observatory.)

Everyone, at some time or anotha, has Been at night a bright shooting star or meteor move across the sky and eventually fade away among the stars. Some of these meteors move very quickly, leaving for a ™ raen * °'*™ I bright trail, while others seem to dawdle and move very bke a sky rocket. , , To astronomers these visitors belong to various swarms ot families, each amlly consisting of a large numbe, :jt small particles travailing, in . space, some ot the individuals of which meet the earth's atmosphere as_ the, earth crosses .their path of flight, and are rendered luminous. A careful watcher will notice that many of the trails observed seem to radiate from one point m the heavens Each family has its own radi ant point, and it is with the object of determining exactly the positions of these radiant points that astronomers observe them at all. To some people the sitting up at night to watch the heavens for meteors may seem rather tedious, and may even be an impossible task owing to other occupations. To these, and especially those who are keen photographers, the employment of a camera in this work makes, the task at once fascinating and interesting. The process is quite simple. On some clear and moonless night place the camera (any camera will do. the larger the better) on some rigid support, either out of doors or on a convenient window sill, pointing the camera directly towards the Polo Star and fixing it securely as a precaution against movement by the wind. The Pole Star can easily be found, as it is situated due north and lies on the prolongation of a line joining-,the two bright stars, known as "the pointers," in the constellation of the Great Bear or Plough. The object in pointing the camera to the Pole Star is that, as the camera is fixed, most of the stars will make their trails completely on the photographic plate and these trails will all be portions of small circles. By comparing such trails with a star--*tlas all the stars can easily be identified. Having thus fixed your camera, and set the focus for some distant object, open the dark slide and take the cap ?£• The camera can then be left for any number of hours: the longer the time the longer will be the trails, and also the greater wiikbe the chance of catching a meteor. Should a bright meteor pass in front of the camera during this interval then its trail will be automatically photographed. The position of the meteor, trail in relation to the star trails can be seen, at a glance and the direction of the radiant point at once determined. The main precautions to be taken are: Select a position where no lights, such as street lamps, are in front of thc_ camera; fix the camera rigidly to avoid vibration: protect the camera and lens from dew by covering them with a simple form of hood; use rapid plates for choice; and do not expose them, on nights when the moon is very bright. On any night of the year there is a chance of photographing an interesting meteor, but, of course, the most favourable nights are those when special swarms are expected, the dates of which can be ascertained from published tables.